buffer.c 88.6 KB
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/*
 *  linux/fs/buffer.c
 *
 *  Copyright (C) 1991, 1992, 2002  Linus Torvalds
 */

/*
 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
 *
 * Removed a lot of unnecessary code and simplified things now that
 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
 *
 * Speed up hash, lru, and free list operations.  Use gfp() for allocating
 * hash table, use SLAB cache for buffer heads. SMP threading.  -DaveM
 *
 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
 *
 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
 */

#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/percpu.h>
#include <linux/slab.h>
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#include <linux/capability.h>
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#include <linux/blkdev.h>
#include <linux/file.h>
#include <linux/quotaops.h>
#include <linux/highmem.h>
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#include <linux/export.h>
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#include <linux/writeback.h>
#include <linux/hash.h>
#include <linux/suspend.h>
#include <linux/buffer_head.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/bio.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/bitops.h>
#include <linux/mpage.h>
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#include <linux/bit_spinlock.h>
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#include <trace/events/block.h>
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static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);

#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)

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void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
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{
	bh->b_end_io = handler;
	bh->b_private = private;
}
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EXPORT_SYMBOL(init_buffer);
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inline void touch_buffer(struct buffer_head *bh)
{
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	trace_block_touch_buffer(bh);
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	mark_page_accessed(bh->b_page);
}
EXPORT_SYMBOL(touch_buffer);

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void __lock_buffer(struct buffer_head *bh)
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{
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	wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
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}
EXPORT_SYMBOL(__lock_buffer);

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void unlock_buffer(struct buffer_head *bh)
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{
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	clear_bit_unlock(BH_Lock, &bh->b_state);
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	smp_mb__after_atomic();
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	wake_up_bit(&bh->b_state, BH_Lock);
}
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EXPORT_SYMBOL(unlock_buffer);
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/*
 * Returns if the page has dirty or writeback buffers. If all the buffers
 * are unlocked and clean then the PageDirty information is stale. If
 * any of the pages are locked, it is assumed they are locked for IO.
 */
void buffer_check_dirty_writeback(struct page *page,
				     bool *dirty, bool *writeback)
{
	struct buffer_head *head, *bh;
	*dirty = false;
	*writeback = false;

	BUG_ON(!PageLocked(page));

	if (!page_has_buffers(page))
		return;

	if (PageWriteback(page))
		*writeback = true;

	head = page_buffers(page);
	bh = head;
	do {
		if (buffer_locked(bh))
			*writeback = true;

		if (buffer_dirty(bh))
			*dirty = true;

		bh = bh->b_this_page;
	} while (bh != head);
}
EXPORT_SYMBOL(buffer_check_dirty_writeback);

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/*
 * Block until a buffer comes unlocked.  This doesn't stop it
 * from becoming locked again - you have to lock it yourself
 * if you want to preserve its state.
 */
void __wait_on_buffer(struct buffer_head * bh)
{
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	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
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}
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EXPORT_SYMBOL(__wait_on_buffer);
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static void
__clear_page_buffers(struct page *page)
{
	ClearPagePrivate(page);
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	set_page_private(page, 0);
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	page_cache_release(page);
}

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static void buffer_io_error(struct buffer_head *bh, char *msg)
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{
	char b[BDEVNAME_SIZE];
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	if (!test_bit(BH_Quiet, &bh->b_state))
		printk_ratelimited(KERN_ERR
			"Buffer I/O error on dev %s, logical block %llu%s\n",
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			bdevname(bh->b_bdev, b),
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			(unsigned long long)bh->b_blocknr, msg);
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}

/*
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 * End-of-IO handler helper function which does not touch the bh after
 * unlocking it.
 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
 * a race there is benign: unlock_buffer() only use the bh's address for
 * hashing after unlocking the buffer, so it doesn't actually touch the bh
 * itself.
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 */
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static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
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{
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		/* This happens, due to failed READA attempts. */
		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
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}

/*
 * Default synchronous end-of-IO handler..  Just mark it up-to-date and
 * unlock the buffer. This is what ll_rw_block uses too.
 */
void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
{
	__end_buffer_read_notouch(bh, uptodate);
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	put_bh(bh);
}
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EXPORT_SYMBOL(end_buffer_read_sync);
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void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
{
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
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		buffer_io_error(bh, ", lost sync page write");
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		set_buffer_write_io_error(bh);
		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
	put_bh(bh);
}
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EXPORT_SYMBOL(end_buffer_write_sync);
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/*
 * Various filesystems appear to want __find_get_block to be non-blocking.
 * But it's the page lock which protects the buffers.  To get around this,
 * we get exclusion from try_to_free_buffers with the blockdev mapping's
 * private_lock.
 *
 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
 * may be quite high.  This code could TryLock the page, and if that
 * succeeds, there is no need to take private_lock. (But if
 * private_lock is contended then so is mapping->tree_lock).
 */
static struct buffer_head *
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__find_get_block_slow(struct block_device *bdev, sector_t block)
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{
	struct inode *bd_inode = bdev->bd_inode;
	struct address_space *bd_mapping = bd_inode->i_mapping;
	struct buffer_head *ret = NULL;
	pgoff_t index;
	struct buffer_head *bh;
	struct buffer_head *head;
	struct page *page;
	int all_mapped = 1;

	index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
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	page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
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	if (!page)
		goto out;

	spin_lock(&bd_mapping->private_lock);
	if (!page_has_buffers(page))
		goto out_unlock;
	head = page_buffers(page);
	bh = head;
	do {
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		if (!buffer_mapped(bh))
			all_mapped = 0;
		else if (bh->b_blocknr == block) {
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			ret = bh;
			get_bh(bh);
			goto out_unlock;
		}
		bh = bh->b_this_page;
	} while (bh != head);

	/* we might be here because some of the buffers on this page are
	 * not mapped.  This is due to various races between
	 * file io on the block device and getblk.  It gets dealt with
	 * elsewhere, don't buffer_error if we had some unmapped buffers
	 */
	if (all_mapped) {
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		char b[BDEVNAME_SIZE];

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		printk("__find_get_block_slow() failed. "
			"block=%llu, b_blocknr=%llu\n",
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			(unsigned long long)block,
			(unsigned long long)bh->b_blocknr);
		printk("b_state=0x%08lx, b_size=%zu\n",
			bh->b_state, bh->b_size);
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		printk("device %s blocksize: %d\n", bdevname(bdev, b),
			1 << bd_inode->i_blkbits);
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	}
out_unlock:
	spin_unlock(&bd_mapping->private_lock);
	page_cache_release(page);
out:
	return ret;
}

/*
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 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
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 */
static void free_more_memory(void)
{
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	struct zone *zone;
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	int nid;
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	wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
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	yield();

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	for_each_online_node(nid) {
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		(void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
						gfp_zone(GFP_NOFS), NULL,
						&zone);
		if (zone)
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			try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
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						GFP_NOFS, NULL);
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	}
}

/*
 * I/O completion handler for block_read_full_page() - pages
 * which come unlocked at the end of I/O.
 */
static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
{
	unsigned long flags;
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	struct buffer_head *first;
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	struct buffer_head *tmp;
	struct page *page;
	int page_uptodate = 1;

	BUG_ON(!buffer_async_read(bh));

	page = bh->b_page;
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		clear_buffer_uptodate(bh);
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		buffer_io_error(bh, ", async page read");
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		SetPageError(page);
	}

	/*
	 * Be _very_ careful from here on. Bad things can happen if
	 * two buffer heads end IO at almost the same time and both
	 * decide that the page is now completely done.
	 */
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	first = page_buffers(page);
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
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	clear_buffer_async_read(bh);
	unlock_buffer(bh);
	tmp = bh;
	do {
		if (!buffer_uptodate(tmp))
			page_uptodate = 0;
		if (buffer_async_read(tmp)) {
			BUG_ON(!buffer_locked(tmp));
			goto still_busy;
		}
		tmp = tmp->b_this_page;
	} while (tmp != bh);
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	/*
	 * If none of the buffers had errors and they are all
	 * uptodate then we can set the page uptodate.
	 */
	if (page_uptodate && !PageError(page))
		SetPageUptodate(page);
	unlock_page(page);
	return;

still_busy:
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	return;
}

/*
 * Completion handler for block_write_full_page() - pages which are unlocked
 * during I/O, and which have PageWriteback cleared upon I/O completion.
 */
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void end_buffer_async_write(struct buffer_head *bh, int uptodate)
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{
	unsigned long flags;
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	struct buffer_head *first;
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	struct buffer_head *tmp;
	struct page *page;

	BUG_ON(!buffer_async_write(bh));

	page = bh->b_page;
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
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		buffer_io_error(bh, ", lost async page write");
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		set_bit(AS_EIO, &page->mapping->flags);
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		set_buffer_write_io_error(bh);
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		clear_buffer_uptodate(bh);
		SetPageError(page);
	}

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	first = page_buffers(page);
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);

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	clear_buffer_async_write(bh);
	unlock_buffer(bh);
	tmp = bh->b_this_page;
	while (tmp != bh) {
		if (buffer_async_write(tmp)) {
			BUG_ON(!buffer_locked(tmp));
			goto still_busy;
		}
		tmp = tmp->b_this_page;
	}
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	end_page_writeback(page);
	return;

still_busy:
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	return;
}
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EXPORT_SYMBOL(end_buffer_async_write);
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/*
 * If a page's buffers are under async readin (end_buffer_async_read
 * completion) then there is a possibility that another thread of
 * control could lock one of the buffers after it has completed
 * but while some of the other buffers have not completed.  This
 * locked buffer would confuse end_buffer_async_read() into not unlocking
 * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
 * that this buffer is not under async I/O.
 *
 * The page comes unlocked when it has no locked buffer_async buffers
 * left.
 *
 * PageLocked prevents anyone starting new async I/O reads any of
 * the buffers.
 *
 * PageWriteback is used to prevent simultaneous writeout of the same
 * page.
 *
 * PageLocked prevents anyone from starting writeback of a page which is
 * under read I/O (PageWriteback is only ever set against a locked page).
 */
static void mark_buffer_async_read(struct buffer_head *bh)
{
	bh->b_end_io = end_buffer_async_read;
	set_buffer_async_read(bh);
}

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static void mark_buffer_async_write_endio(struct buffer_head *bh,
					  bh_end_io_t *handler)
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{
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	bh->b_end_io = handler;
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	set_buffer_async_write(bh);
}
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void mark_buffer_async_write(struct buffer_head *bh)
{
	mark_buffer_async_write_endio(bh, end_buffer_async_write);
}
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EXPORT_SYMBOL(mark_buffer_async_write);


/*
 * fs/buffer.c contains helper functions for buffer-backed address space's
 * fsync functions.  A common requirement for buffer-based filesystems is
 * that certain data from the backing blockdev needs to be written out for
 * a successful fsync().  For example, ext2 indirect blocks need to be
 * written back and waited upon before fsync() returns.
 *
 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
 * management of a list of dependent buffers at ->i_mapping->private_list.
 *
 * Locking is a little subtle: try_to_free_buffers() will remove buffers
 * from their controlling inode's queue when they are being freed.  But
 * try_to_free_buffers() will be operating against the *blockdev* mapping
 * at the time, not against the S_ISREG file which depends on those buffers.
 * So the locking for private_list is via the private_lock in the address_space
 * which backs the buffers.  Which is different from the address_space 
 * against which the buffers are listed.  So for a particular address_space,
 * mapping->private_lock does *not* protect mapping->private_list!  In fact,
 * mapping->private_list will always be protected by the backing blockdev's
 * ->private_lock.
 *
 * Which introduces a requirement: all buffers on an address_space's
 * ->private_list must be from the same address_space: the blockdev's.
 *
 * address_spaces which do not place buffers at ->private_list via these
 * utility functions are free to use private_lock and private_list for
 * whatever they want.  The only requirement is that list_empty(private_list)
 * be true at clear_inode() time.
 *
 * FIXME: clear_inode should not call invalidate_inode_buffers().  The
 * filesystems should do that.  invalidate_inode_buffers() should just go
 * BUG_ON(!list_empty).
 *
 * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
 * take an address_space, not an inode.  And it should be called
 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
 * queued up.
 *
 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
 * list if it is already on a list.  Because if the buffer is on a list,
 * it *must* already be on the right one.  If not, the filesystem is being
 * silly.  This will save a ton of locking.  But first we have to ensure
 * that buffers are taken *off* the old inode's list when they are freed
 * (presumably in truncate).  That requires careful auditing of all
 * filesystems (do it inside bforget()).  It could also be done by bringing
 * b_inode back.
 */

/*
 * The buffer's backing address_space's private_lock must be held
 */
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static void __remove_assoc_queue(struct buffer_head *bh)
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{
	list_del_init(&bh->b_assoc_buffers);
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	WARN_ON(!bh->b_assoc_map);
	if (buffer_write_io_error(bh))
		set_bit(AS_EIO, &bh->b_assoc_map->flags);
	bh->b_assoc_map = NULL;
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}

int inode_has_buffers(struct inode *inode)
{
	return !list_empty(&inode->i_data.private_list);
}

/*
 * osync is designed to support O_SYNC io.  It waits synchronously for
 * all already-submitted IO to complete, but does not queue any new
 * writes to the disk.
 *
 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
 * you dirty the buffers, and then use osync_inode_buffers to wait for
 * completion.  Any other dirty buffers which are not yet queued for
 * write will not be flushed to disk by the osync.
 */
static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
{
	struct buffer_head *bh;
	struct list_head *p;
	int err = 0;

	spin_lock(lock);
repeat:
	list_for_each_prev(p, list) {
		bh = BH_ENTRY(p);
		if (buffer_locked(bh)) {
			get_bh(bh);
			spin_unlock(lock);
			wait_on_buffer(bh);
			if (!buffer_uptodate(bh))
				err = -EIO;
			brelse(bh);
			spin_lock(lock);
			goto repeat;
		}
	}
	spin_unlock(lock);
	return err;
}

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static void do_thaw_one(struct super_block *sb, void *unused)
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{
	char b[BDEVNAME_SIZE];
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	while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
		printk(KERN_WARNING "Emergency Thaw on %s\n",
		       bdevname(sb->s_bdev, b));
}
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static void do_thaw_all(struct work_struct *work)
{
	iterate_supers(do_thaw_one, NULL);
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	kfree(work);
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	printk(KERN_WARNING "Emergency Thaw complete\n");
}

/**
 * emergency_thaw_all -- forcibly thaw every frozen filesystem
 *
 * Used for emergency unfreeze of all filesystems via SysRq
 */
void emergency_thaw_all(void)
{
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	struct work_struct *work;

	work = kmalloc(sizeof(*work), GFP_ATOMIC);
	if (work) {
		INIT_WORK(work, do_thaw_all);
		schedule_work(work);
	}
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}

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/**
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 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
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 * @mapping: the mapping which wants those buffers written
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 *
 * Starts I/O against the buffers at mapping->private_list, and waits upon
 * that I/O.
 *
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 * Basically, this is a convenience function for fsync().
 * @mapping is a file or directory which needs those buffers to be written for
 * a successful fsync().
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 */
int sync_mapping_buffers(struct address_space *mapping)
{
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	struct address_space *buffer_mapping = mapping->private_data;
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	if (buffer_mapping == NULL || list_empty(&mapping->private_list))
		return 0;

	return fsync_buffers_list(&buffer_mapping->private_lock,
					&mapping->private_list);
}
EXPORT_SYMBOL(sync_mapping_buffers);

/*
 * Called when we've recently written block `bblock', and it is known that
 * `bblock' was for a buffer_boundary() buffer.  This means that the block at
 * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
 * dirty, schedule it for IO.  So that indirects merge nicely with their data.
 */
void write_boundary_block(struct block_device *bdev,
			sector_t bblock, unsigned blocksize)
{
	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
	if (bh) {
		if (buffer_dirty(bh))
			ll_rw_block(WRITE, 1, &bh);
		put_bh(bh);
	}
}

void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
{
	struct address_space *mapping = inode->i_mapping;
	struct address_space *buffer_mapping = bh->b_page->mapping;

	mark_buffer_dirty(bh);
605 606
	if (!mapping->private_data) {
		mapping->private_data = buffer_mapping;
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	} else {
608
		BUG_ON(mapping->private_data != buffer_mapping);
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	}
610
	if (!bh->b_assoc_map) {
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		spin_lock(&buffer_mapping->private_lock);
		list_move_tail(&bh->b_assoc_buffers,
				&mapping->private_list);
614
		bh->b_assoc_map = mapping;
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		spin_unlock(&buffer_mapping->private_lock);
	}
}
EXPORT_SYMBOL(mark_buffer_dirty_inode);

620 621 622 623 624 625 626
/*
 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
 * dirty.
 *
 * If warn is true, then emit a warning if the page is not uptodate and has
 * not been truncated.
 */
627
static void __set_page_dirty(struct page *page,
628 629
		struct address_space *mapping, int warn)
{
630 631 632
	unsigned long flags;

	spin_lock_irqsave(&mapping->tree_lock, flags);
633 634
	if (page->mapping) {	/* Race with truncate? */
		WARN_ON_ONCE(warn && !PageUptodate(page));
635
		account_page_dirtied(page, mapping);
636 637 638
		radix_tree_tag_set(&mapping->page_tree,
				page_index(page), PAGECACHE_TAG_DIRTY);
	}
639
	spin_unlock_irqrestore(&mapping->tree_lock, flags);
640 641 642
	__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
}

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/*
 * Add a page to the dirty page list.
 *
 * It is a sad fact of life that this function is called from several places
 * deeply under spinlocking.  It may not sleep.
 *
 * If the page has buffers, the uptodate buffers are set dirty, to preserve
 * dirty-state coherency between the page and the buffers.  It the page does
 * not have buffers then when they are later attached they will all be set
 * dirty.
 *
 * The buffers are dirtied before the page is dirtied.  There's a small race
 * window in which a writepage caller may see the page cleanness but not the
 * buffer dirtiness.  That's fine.  If this code were to set the page dirty
 * before the buffers, a concurrent writepage caller could clear the page dirty
 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
 * page on the dirty page list.
 *
 * We use private_lock to lock against try_to_free_buffers while using the
 * page's buffer list.  Also use this to protect against clean buffers being
 * added to the page after it was set dirty.
 *
 * FIXME: may need to call ->reservepage here as well.  That's rather up to the
 * address_space though.
 */
int __set_page_dirty_buffers(struct page *page)
{
670
	int newly_dirty;
671
	struct address_space *mapping = page_mapping(page);
672 673 674

	if (unlikely(!mapping))
		return !TestSetPageDirty(page);
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	spin_lock(&mapping->private_lock);
	if (page_has_buffers(page)) {
		struct buffer_head *head = page_buffers(page);
		struct buffer_head *bh = head;

		do {
			set_buffer_dirty(bh);
			bh = bh->b_this_page;
		} while (bh != head);
	}
686
	newly_dirty = !TestSetPageDirty(page);
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	spin_unlock(&mapping->private_lock);

689 690 691
	if (newly_dirty)
		__set_page_dirty(page, mapping, 1);
	return newly_dirty;
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}
EXPORT_SYMBOL(__set_page_dirty_buffers);

/*
 * Write out and wait upon a list of buffers.
 *
 * We have conflicting pressures: we want to make sure that all
 * initially dirty buffers get waited on, but that any subsequently
 * dirtied buffers don't.  After all, we don't want fsync to last
 * forever if somebody is actively writing to the file.
 *
 * Do this in two main stages: first we copy dirty buffers to a
 * temporary inode list, queueing the writes as we go.  Then we clean
 * up, waiting for those writes to complete.
 * 
 * During this second stage, any subsequent updates to the file may end
 * up refiling the buffer on the original inode's dirty list again, so
 * there is a chance we will end up with a buffer queued for write but
 * not yet completed on that list.  So, as a final cleanup we go through
 * the osync code to catch these locked, dirty buffers without requeuing
 * any newly dirty buffers for write.
 */
static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
{
	struct buffer_head *bh;
	struct list_head tmp;
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	struct address_space *mapping;
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	int err = 0, err2;
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	struct blk_plug plug;
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	INIT_LIST_HEAD(&tmp);
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	blk_start_plug(&plug);
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	spin_lock(lock);
	while (!list_empty(list)) {
		bh = BH_ENTRY(list->next);
728
		mapping = bh->b_assoc_map;
729
		__remove_assoc_queue(bh);
730 731 732
		/* Avoid race with mark_buffer_dirty_inode() which does
		 * a lockless check and we rely on seeing the dirty bit */
		smp_mb();
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		if (buffer_dirty(bh) || buffer_locked(bh)) {
			list_add(&bh->b_assoc_buffers, &tmp);
735
			bh->b_assoc_map = mapping;
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			if (buffer_dirty(bh)) {
				get_bh(bh);
				spin_unlock(lock);
				/*
				 * Ensure any pending I/O completes so that
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				 * write_dirty_buffer() actually writes the
				 * current contents - it is a noop if I/O is
				 * still in flight on potentially older
				 * contents.
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				 */
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				write_dirty_buffer(bh, WRITE_SYNC);
747 748 749 750 751 752 753

				/*
				 * Kick off IO for the previous mapping. Note
				 * that we will not run the very last mapping,
				 * wait_on_buffer() will do that for us
				 * through sync_buffer().
				 */
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				brelse(bh);
				spin_lock(lock);
			}
		}
	}

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	spin_unlock(lock);
	blk_finish_plug(&plug);
	spin_lock(lock);

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	while (!list_empty(&tmp)) {
		bh = BH_ENTRY(tmp.prev);
		get_bh(bh);
767 768 769 770 771 772 773
		mapping = bh->b_assoc_map;
		__remove_assoc_queue(bh);
		/* Avoid race with mark_buffer_dirty_inode() which does
		 * a lockless check and we rely on seeing the dirty bit */
		smp_mb();
		if (buffer_dirty(bh)) {
			list_add(&bh->b_assoc_buffers,
774
				 &mapping->private_list);
775 776
			bh->b_assoc_map = mapping;
		}
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		spin_unlock(lock);
		wait_on_buffer(bh);
		if (!buffer_uptodate(bh))
			err = -EIO;
		brelse(bh);
		spin_lock(lock);
	}
	
	spin_unlock(lock);
	err2 = osync_buffers_list(lock, list);
	if (err)
		return err;
	else
		return err2;
}

/*
 * Invalidate any and all dirty buffers on a given inode.  We are
 * probably unmounting the fs, but that doesn't mean we have already
 * done a sync().  Just drop the buffers from the inode list.
 *
 * NOTE: we take the inode's blockdev's mapping's private_lock.  Which
 * assumes that all the buffers are against the blockdev.  Not true
 * for reiserfs.
 */
void invalidate_inode_buffers(struct inode *inode)
{
	if (inode_has_buffers(inode)) {
		struct address_space *mapping = &inode->i_data;
		struct list_head *list = &mapping->private_list;
807
		struct address_space *buffer_mapping = mapping->private_data;
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		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list))
			__remove_assoc_queue(BH_ENTRY(list->next));
		spin_unlock(&buffer_mapping->private_lock);
	}
}
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EXPORT_SYMBOL(invalidate_inode_buffers);
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/*
 * Remove any clean buffers from the inode's buffer list.  This is called
 * when we're trying to free the inode itself.  Those buffers can pin it.
 *
 * Returns true if all buffers were removed.
 */
int remove_inode_buffers(struct inode *inode)
{
	int ret = 1;

	if (inode_has_buffers(inode)) {
		struct address_space *mapping = &inode->i_data;
		struct list_head *list = &mapping->private_list;
830
		struct address_space *buffer_mapping = mapping->private_data;
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		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list)) {
			struct buffer_head *bh = BH_ENTRY(list->next);
			if (buffer_dirty(bh)) {
				ret = 0;
				break;
			}
			__remove_assoc_queue(bh);
		}
		spin_unlock(&buffer_mapping->private_lock);
	}
	return ret;
}

/*
 * Create the appropriate buffers when given a page for data area and
 * the size of each buffer.. Use the bh->b_this_page linked list to
 * follow the buffers created.  Return NULL if unable to create more
 * buffers.
 *
 * The retry flag is used to differentiate async IO (paging, swapping)
 * which may not fail from ordinary buffer allocations.
 */
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
		int retry)
{
	struct buffer_head *bh, *head;
	long offset;

try_again:
	head = NULL;
	offset = PAGE_SIZE;
	while ((offset -= size) >= 0) {
		bh = alloc_buffer_head(GFP_NOFS);
		if (!bh)
			goto no_grow;

		bh->b_this_page = head;
		bh->b_blocknr = -1;
		head = bh;

		bh->b_size = size;

		/* Link the buffer to its page */
		set_bh_page(bh, page, offset);
	}
	return head;
/*
 * In case anything failed, we just free everything we got.
 */
no_grow:
	if (head) {
		do {
			bh = head;
			head = head->b_this_page;
			free_buffer_head(bh);
		} while (head);
	}

	/*
	 * Return failure for non-async IO requests.  Async IO requests
	 * are not allowed to fail, so we have to wait until buffer heads
	 * become available.  But we don't want tasks sleeping with 
	 * partially complete buffers, so all were released above.
	 */
	if (!retry)
		return NULL;

	/* We're _really_ low on memory. Now we just
	 * wait for old buffer heads to become free due to
	 * finishing IO.  Since this is an async request and
	 * the reserve list is empty, we're sure there are 
	 * async buffer heads in use.
	 */
	free_more_memory();
	goto try_again;
}
EXPORT_SYMBOL_GPL(alloc_page_buffers);

static inline void
link_dev_buffers(struct page *page, struct buffer_head *head)
{
	struct buffer_head *bh, *tail;

	bh = head;
	do {
		tail = bh;
		bh = bh->b_this_page;
	} while (bh);
	tail->b_this_page = head;
	attach_page_buffers(page, head);
}

925 926 927 928 929 930 931 932 933 934 935 936
static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
{
	sector_t retval = ~((sector_t)0);
	loff_t sz = i_size_read(bdev->bd_inode);

	if (sz) {
		unsigned int sizebits = blksize_bits(size);
		retval = (sz >> sizebits);
	}
	return retval;
}

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/*
 * Initialise the state of a blockdev page's buffers.
 */ 
940
static sector_t
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init_page_buffers(struct page *page, struct block_device *bdev,
			sector_t block, int size)
{
	struct buffer_head *head = page_buffers(page);
	struct buffer_head *bh = head;
	int uptodate = PageUptodate(page);
947
	sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
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	do {
		if (!buffer_mapped(bh)) {
			init_buffer(bh, NULL, NULL);
			bh->b_bdev = bdev;
			bh->b_blocknr = block;
			if (uptodate)
				set_buffer_uptodate(bh);
956 957
			if (block < end_block)
				set_buffer_mapped(bh);
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		}
		block++;
		bh = bh->b_this_page;
	} while (bh != head);
962 963 964 965 966

	/*
	 * Caller needs to validate requested block against end of device.
	 */
	return end_block;
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}

/*
 * Create the page-cache page that contains the requested block.
 *
972
 * This is used purely for blockdev mappings.
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 */
974
static int
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grow_dev_page(struct block_device *bdev, sector_t block,
976
	      pgoff_t index, int size, int sizebits, gfp_t gfp)
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{
	struct inode *inode = bdev->bd_inode;
	struct page *page;
	struct buffer_head *bh;
981 982
	sector_t end_block;
	int ret = 0;		/* Will call free_more_memory() */
983
	gfp_t gfp_mask;
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985 986
	gfp_mask = (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS) | gfp;

987 988 989 990 991 992 993 994 995
	/*
	 * XXX: __getblk_slow() can not really deal with failure and
	 * will endlessly loop on improvised global reclaim.  Prefer
	 * looping in the allocator rather than here, at least that
	 * code knows what it's doing.
	 */
	gfp_mask |= __GFP_NOFAIL;

	page = find_or_create_page(inode->i_mapping, index, gfp_mask);
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	if (!page)
997
		return ret;
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999
	BUG_ON(!PageLocked(page));
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	if (page_has_buffers(page)) {
		bh = page_buffers(page);
		if (bh->b_size == size) {
1004
			end_block = init_page_buffers(page, bdev,
1005 1006
						(sector_t)index << sizebits,
						size);
1007
			goto done;
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		}
		if (!try_to_free_buffers(page))
			goto failed;
	}

	/*
	 * Allocate some buffers for this page
	 */
	bh = alloc_page_buffers(page, size, 0);
	if (!bh)
		goto failed;

	/*
	 * Link the page to the buffers and initialise them.  Take the
	 * lock to be atomic wrt __find_get_block(), which does not
	 * run under the page lock.
	 */
	spin_lock(&inode->i_mapping->private_lock);
	link_dev_buffers(page, bh);
1027 1028
	end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
			size);
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	spin_unlock(&inode->i_mapping->private_lock);
1030 1031
done:
	ret = (block < end_block) ? 1 : -ENXIO;
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failed:
	unlock_page(page);
	page_cache_release(page);
1035
	return ret;
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}

/*
 * Create buffers for the specified block device block's page.  If
 * that page was dirty, the buffers are set dirty also.
 */
1042
static int
1043
grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
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{
	pgoff_t index;
	int sizebits;

	sizebits = -1;
	do {
		sizebits++;
	} while ((size << sizebits) < PAGE_SIZE);

	index = block >> sizebits;

1055 1056 1057 1058 1059 1060 1061 1062 1063
	/*
	 * Check for a block which wants to lie outside our maximum possible
	 * pagecache index.  (this comparison is done using sector_t types).
	 */
	if (unlikely(index != block >> sizebits)) {
		char b[BDEVNAME_SIZE];

		printk(KERN_ERR "%s: requested out-of-range block %llu for "
			"device %s\n",
1064
			__func__, (unsigned long long)block,
1065 1066 1067
			bdevname(bdev, b));
		return -EIO;
	}
1068

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	/* Create a page with the proper size buffers.. */
1070
	return grow_dev_page(bdev, block, index, size, sizebits, gfp);
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}

1073 1074 1075
struct buffer_head *
__getblk_slow(struct block_device *bdev, sector_t block,
	     unsigned size, gfp_t gfp)
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{
	/* Size must be multiple of hard sectorsize */
1078
	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
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			(size < 512 || size > PAGE_SIZE))) {
		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
					size);
1082 1083
		printk(KERN_ERR "logical block size: %d\n",
					bdev_logical_block_size(bdev));
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		dump_stack();
		return NULL;
	}

1089 1090 1091
	for (;;) {
		struct buffer_head *bh;
		int ret;
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		bh = __find_get_block(bdev, block, size);
		if (bh)
			return bh;
1096

1097
		ret = grow_buffers(bdev, block, size, gfp);
1098 1099 1100 1101
		if (ret < 0)
			return NULL;
		if (ret == 0)
			free_more_memory();
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	}
}
1104
EXPORT_SYMBOL(__getblk_slow);
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/*
 * The relationship between dirty buffers and dirty pages:
 *
 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
 * the page is tagged dirty in its radix tree.
 *
 * At all times, the dirtiness of the buffers represents the dirtiness of
 * subsections of the page.  If the page has buffers, the page dirty bit is
 * merely a hint about the true dirty state.
 *
 * When a page is set dirty in its entirety, all its buffers are marked dirty
 * (if the page has buffers).
 *
 * When a buffer is marked dirty, its page is dirtied, but the page's other
 * buffers are not.
 *
 * Also.  When blockdev buffers are explicitly read with bread(), they
 * individually become uptodate.  But their backing page remains not
 * uptodate - even if all of its buffers are uptodate.  A subsequent
 * block_read_full_page() against that page will discover all the uptodate
 * buffers, will set the page uptodate and will perform no I/O.
 */

/**
 * mark_buffer_dirty - mark a buffer_head as needing writeout
1131
 * @bh: the buffer_head to mark dirty
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 *
 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
 * backing page dirty, then tag the page as dirty in its address_space's radix
 * tree and then attach the address_space's inode to its superblock's dirty
 * inode list.
 *
 * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
1139
 * mapping->tree_lock and mapping->host->i_lock.
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 */
1141
void mark_buffer_dirty(struct buffer_head *bh)
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{
1143
	WARN_ON_ONCE(!buffer_uptodate(bh));
1144

1145 1146
	trace_block_dirty_buffer(bh);

1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158
	/*
	 * Very *carefully* optimize the it-is-already-dirty case.
	 *
	 * Don't let the final "is it dirty" escape to before we
	 * perhaps modified the buffer.
	 */
	if (buffer_dirty(bh)) {
		smp_mb();
		if (buffer_dirty(bh))
			return;
	}

1159 1160
	if (!test_set_buffer_dirty(bh)) {
		struct page *page = bh->b_page;
1161 1162 1163 1164 1165
		if (!TestSetPageDirty(page)) {
			struct address_space *mapping = page_mapping(page);
			if (mapping)
				__set_page_dirty(page, mapping, 0);
		}
1166
	}
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}
1168
EXPORT_SYMBOL(mark_buffer_dirty);
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/*
 * Decrement a buffer_head's reference count.  If all buffers against a page
 * have zero reference count, are clean and unlocked, and if the page is clean
 * and unlocked then try_to_free_buffers() may strip the buffers from the page
 * in preparation for freeing it (sometimes, rarely, buffers are removed from
 * a page but it ends up not being freed, and buffers may later be reattached).
 */
void __brelse(struct buffer_head * buf)
{
	if (atomic_read(&buf->b_count)) {
		put_bh(buf);
		return;
	}
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Arjan van de Ven 已提交
1183
	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
L
Linus Torvalds 已提交
1184
}
1185
EXPORT_SYMBOL(__brelse);
L
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1186 1187 1188 1189 1190 1191 1192 1193

/*
 * bforget() is like brelse(), except it discards any
 * potentially dirty data.
 */
void __bforget(struct buffer_head *bh)
{
	clear_buffer_dirty(bh);
1194
	if (bh->b_assoc_map) {
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		struct address_space *buffer_mapping = bh->b_page->mapping;

		spin_lock(&buffer_mapping->private_lock);
		list_del_init(&bh->b_assoc_buffers);
1199
		bh->b_assoc_map = NULL;
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		spin_unlock(&buffer_mapping->private_lock);
	}
	__brelse(bh);
}
1204
EXPORT_SYMBOL(__bforget);
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static struct buffer_head *__bread_slow(struct buffer_head *bh)
{
	lock_buffer(bh);
	if (buffer_uptodate(bh)) {
		unlock_buffer(bh);
		return bh;
	} else {
		get_bh(bh);
		bh->b_end_io = end_buffer_read_sync;
		submit_bh(READ, bh);
		wait_on_buffer(bh);
		if (buffer_uptodate(bh))
			return bh;
	}
	brelse(bh);
	return NULL;
}

/*
 * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
 * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
 * refcount elevated by one when they're in an LRU.  A buffer can only appear
 * once in a particular CPU's LRU.  A single buffer can be present in multiple
 * CPU's LRUs at the same time.
 *
 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
 * sb_find_get_block().
 *
 * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
 * a local interrupt disable for that.
 */

1238
#define BH_LRU_SIZE	16
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struct bh_lru {
	struct buffer_head *bhs[BH_LRU_SIZE];
};

static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};

#ifdef CONFIG_SMP
#define bh_lru_lock()	local_irq_disable()
#define bh_lru_unlock()	local_irq_enable()
#else
#define bh_lru_lock()	preempt_disable()
#define bh_lru_unlock()	preempt_enable()
#endif

static inline void check_irqs_on(void)
{
#ifdef irqs_disabled
	BUG_ON(irqs_disabled());
#endif
}

/*
 * The LRU management algorithm is dopey-but-simple.  Sorry.
 */
static void bh_lru_install(struct buffer_head *bh)
{
	struct buffer_head *evictee = NULL;

	check_irqs_on();
	bh_lru_lock();
1270
	if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
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		struct buffer_head *bhs[BH_LRU_SIZE];
		int in;
		int out = 0;

		get_bh(bh);
		bhs[out++] = bh;
		for (in = 0; in < BH_LRU_SIZE; in++) {
1278 1279
			struct buffer_head *bh2 =
				__this_cpu_read(bh_lrus.bhs[in]);
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1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293

			if (bh2 == bh) {
				__brelse(bh2);
			} else {
				if (out >= BH_LRU_SIZE) {
					BUG_ON(evictee != NULL);
					evictee = bh2;
				} else {
					bhs[out++] = bh2;
				}
			}
		}
		while (out < BH_LRU_SIZE)
			bhs[out++] = NULL;
1294
		memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
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	}
	bh_lru_unlock();

	if (evictee)
		__brelse(evictee);
}

/*
 * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
 */
1305
static struct buffer_head *
1306
lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
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1307 1308
{
	struct buffer_head *ret = NULL;
1309
	unsigned int i;
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	check_irqs_on();
	bh_lru_lock();
	for (i = 0; i < BH_LRU_SIZE; i++) {
1314
		struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
L
Linus Torvalds 已提交
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1316 1317
		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
		    bh->b_size == size) {
L
Linus Torvalds 已提交
1318 1319
			if (i) {
				while (i) {
1320 1321
					__this_cpu_write(bh_lrus.bhs[i],
						__this_cpu_read(bh_lrus.bhs[i - 1]));
L
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1322 1323
					i--;
				}
1324
				__this_cpu_write(bh_lrus.bhs[0], bh);
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1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340
			}
			get_bh(bh);
			ret = bh;
			break;
		}
	}
	bh_lru_unlock();
	return ret;
}

/*
 * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
 * it in the LRU and mark it as accessed.  If it is not present then return
 * NULL
 */
struct buffer_head *
1341
__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
L
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1342 1343 1344 1345
{
	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);

	if (bh == NULL) {
1346
		/* __find_get_block_slow will mark the page accessed */
1347
		bh = __find_get_block_slow(bdev, block);
L
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1348 1349
		if (bh)
			bh_lru_install(bh);
1350
	} else
L
Linus Torvalds 已提交
1351
		touch_buffer(bh);
1352

L
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1353 1354 1355 1356 1357
	return bh;
}
EXPORT_SYMBOL(__find_get_block);

/*
1358
 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
L
Linus Torvalds 已提交
1359 1360 1361
 * which corresponds to the passed block_device, block and size. The
 * returned buffer has its reference count incremented.
 *
1362 1363
 * __getblk_gfp() will lock up the machine if grow_dev_page's
 * try_to_free_buffers() attempt is failing.  FIXME, perhaps?
L
Linus Torvalds 已提交
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 */
struct buffer_head *
1366 1367
__getblk_gfp(struct block_device *bdev, sector_t block,
	     unsigned size, gfp_t gfp)
L
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1368 1369 1370 1371 1372
{
	struct buffer_head *bh = __find_get_block(bdev, block, size);

	might_sleep();
	if (bh == NULL)
1373
		bh = __getblk_slow(bdev, block, size, gfp);
L
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1374 1375
	return bh;
}
1376
EXPORT_SYMBOL(__getblk_gfp);
L
Linus Torvalds 已提交
1377 1378 1379 1380

/*
 * Do async read-ahead on a buffer..
 */
1381
void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1382 1383
{
	struct buffer_head *bh = __getblk(bdev, block, size);
A
Andrew Morton 已提交
1384 1385 1386 1387
	if (likely(bh)) {
		ll_rw_block(READA, 1, &bh);
		brelse(bh);
	}
L
Linus Torvalds 已提交
1388 1389 1390 1391
}
EXPORT_SYMBOL(__breadahead);

/**
1392
 *  __bread_gfp() - reads a specified block and returns the bh
1393
 *  @bdev: the block_device to read from
L
Linus Torvalds 已提交
1394 1395
 *  @block: number of block
 *  @size: size (in bytes) to read
1396 1397
 *  @gfp: page allocation flag
 *
L
Linus Torvalds 已提交
1398
 *  Reads a specified block, and returns buffer head that contains it.
1399 1400
 *  The page cache can be allocated from non-movable area
 *  not to prevent page migration if you set gfp to zero.
L
Linus Torvalds 已提交
1401 1402 1403
 *  It returns NULL if the block was unreadable.
 */
struct buffer_head *
1404 1405
__bread_gfp(struct block_device *bdev, sector_t block,
		   unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1406
{
1407
	struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
L
Linus Torvalds 已提交
1408

A
Andrew Morton 已提交
1409
	if (likely(bh) && !buffer_uptodate(bh))
L
Linus Torvalds 已提交
1410 1411 1412
		bh = __bread_slow(bh);
	return bh;
}
1413
EXPORT_SYMBOL(__bread_gfp);
L
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1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430

/*
 * invalidate_bh_lrus() is called rarely - but not only at unmount.
 * This doesn't race because it runs in each cpu either in irq
 * or with preempt disabled.
 */
static void invalidate_bh_lru(void *arg)
{
	struct bh_lru *b = &get_cpu_var(bh_lrus);
	int i;

	for (i = 0; i < BH_LRU_SIZE; i++) {
		brelse(b->bhs[i]);
		b->bhs[i] = NULL;
	}
	put_cpu_var(bh_lrus);
}
1431 1432 1433 1434 1435

static bool has_bh_in_lru(int cpu, void *dummy)
{
	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
	int i;
L
Linus Torvalds 已提交
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1437 1438 1439 1440 1441 1442 1443 1444
	for (i = 0; i < BH_LRU_SIZE; i++) {
		if (b->bhs[i])
			return 1;
	}

	return 0;
}

P
Peter Zijlstra 已提交
1445
void invalidate_bh_lrus(void)
L
Linus Torvalds 已提交
1446
{
1447
	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
L
Linus Torvalds 已提交
1448
}
N
Nick Piggin 已提交
1449
EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
L
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1450 1451 1452 1453 1454

void set_bh_page(struct buffer_head *bh,
		struct page *page, unsigned long offset)
{
	bh->b_page = page;
1455
	BUG_ON(offset >= PAGE_SIZE);
L
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1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468
	if (PageHighMem(page))
		/*
		 * This catches illegal uses and preserves the offset:
		 */
		bh->b_data = (char *)(0 + offset);
	else
		bh->b_data = page_address(page) + offset;
}
EXPORT_SYMBOL(set_bh_page);

/*
 * Called when truncating a buffer on a page completely.
 */
1469 1470 1471 1472 1473 1474

/* Bits that are cleared during an invalidate */
#define BUFFER_FLAGS_DISCARD \
	(1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
	 1 << BH_Delay | 1 << BH_Unwritten)

1475
static void discard_buffer(struct buffer_head * bh)
L
Linus Torvalds 已提交
1476
{
1477 1478
	unsigned long b_state, b_state_old;

L
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1479 1480 1481
	lock_buffer(bh);
	clear_buffer_dirty(bh);
	bh->b_bdev = NULL;
1482 1483 1484 1485 1486 1487 1488 1489
	b_state = bh->b_state;
	for (;;) {
		b_state_old = cmpxchg(&bh->b_state, b_state,
				      (b_state & ~BUFFER_FLAGS_DISCARD));
		if (b_state_old == b_state)
			break;
		b_state = b_state_old;
	}
L
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1490 1491 1492 1493
	unlock_buffer(bh);
}

/**
1494
 * block_invalidatepage - invalidate part or all of a buffer-backed page
L
Linus Torvalds 已提交
1495 1496
 *
 * @page: the page which is affected
1497 1498
 * @offset: start of the range to invalidate
 * @length: length of the range to invalidate
L
Linus Torvalds 已提交
1499 1500
 *
 * block_invalidatepage() is called when all or part of the page has become
1501
 * invalidated by a truncate operation.
L
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1502 1503 1504 1505 1506 1507 1508
 *
 * block_invalidatepage() does not have to release all buffers, but it must
 * ensure that no dirty buffer is left outside @offset and that no I/O
 * is underway against any of the blocks which are outside the truncation
 * point.  Because the caller is about to free (and possibly reuse) those
 * blocks on-disk.
 */
1509 1510
void block_invalidatepage(struct page *page, unsigned int offset,
			  unsigned int length)
L
Linus Torvalds 已提交
1511 1512 1513
{
	struct buffer_head *head, *bh, *next;
	unsigned int curr_off = 0;
1514
	unsigned int stop = length + offset;
L
Linus Torvalds 已提交
1515 1516 1517 1518 1519

	BUG_ON(!PageLocked(page));
	if (!page_has_buffers(page))
		goto out;

1520 1521 1522 1523 1524
	/*
	 * Check for overflow
	 */
	BUG_ON(stop > PAGE_CACHE_SIZE || stop < length);

L
Linus Torvalds 已提交
1525 1526 1527 1528 1529 1530
	head = page_buffers(page);
	bh = head;
	do {
		unsigned int next_off = curr_off + bh->b_size;
		next = bh->b_this_page;

1531 1532 1533 1534 1535 1536
		/*
		 * Are we still fully in range ?
		 */
		if (next_off > stop)
			goto out;

L
Linus Torvalds 已提交
1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551
		/*
		 * is this block fully invalidated?
		 */
		if (offset <= curr_off)
			discard_buffer(bh);
		curr_off = next_off;
		bh = next;
	} while (bh != head);

	/*
	 * We release buffers only if the entire page is being invalidated.
	 * The get_block cached value has been unconditionally invalidated,
	 * so real IO is not possible anymore.
	 */
	if (offset == 0)
1552
		try_to_release_page(page, 0);
L
Linus Torvalds 已提交
1553
out:
1554
	return;
L
Linus Torvalds 已提交
1555 1556 1557
}
EXPORT_SYMBOL(block_invalidatepage);

1558

L
Linus Torvalds 已提交
1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615
/*
 * We attach and possibly dirty the buffers atomically wrt
 * __set_page_dirty_buffers() via private_lock.  try_to_free_buffers
 * is already excluded via the page lock.
 */
void create_empty_buffers(struct page *page,
			unsigned long blocksize, unsigned long b_state)
{
	struct buffer_head *bh, *head, *tail;

	head = alloc_page_buffers(page, blocksize, 1);
	bh = head;
	do {
		bh->b_state |= b_state;
		tail = bh;
		bh = bh->b_this_page;
	} while (bh);
	tail->b_this_page = head;

	spin_lock(&page->mapping->private_lock);
	if (PageUptodate(page) || PageDirty(page)) {
		bh = head;
		do {
			if (PageDirty(page))
				set_buffer_dirty(bh);
			if (PageUptodate(page))
				set_buffer_uptodate(bh);
			bh = bh->b_this_page;
		} while (bh != head);
	}
	attach_page_buffers(page, head);
	spin_unlock(&page->mapping->private_lock);
}
EXPORT_SYMBOL(create_empty_buffers);

/*
 * We are taking a block for data and we don't want any output from any
 * buffer-cache aliases starting from return from that function and
 * until the moment when something will explicitly mark the buffer
 * dirty (hopefully that will not happen until we will free that block ;-)
 * We don't even need to mark it not-uptodate - nobody can expect
 * anything from a newly allocated buffer anyway. We used to used
 * unmap_buffer() for such invalidation, but that was wrong. We definitely
 * don't want to mark the alias unmapped, for example - it would confuse
 * anyone who might pick it with bread() afterwards...
 *
 * Also..  Note that bforget() doesn't lock the buffer.  So there can
 * be writeout I/O going on against recently-freed buffers.  We don't
 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
 * only if we really need to.  That happens here.
 */
void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
{
	struct buffer_head *old_bh;

	might_sleep();

1616
	old_bh = __find_get_block_slow(bdev, block);
L
Linus Torvalds 已提交
1617 1618 1619 1620 1621 1622 1623 1624 1625
	if (old_bh) {
		clear_buffer_dirty(old_bh);
		wait_on_buffer(old_bh);
		clear_buffer_req(old_bh);
		__brelse(old_bh);
	}
}
EXPORT_SYMBOL(unmap_underlying_metadata);

1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647
/*
 * Size is a power-of-two in the range 512..PAGE_SIZE,
 * and the case we care about most is PAGE_SIZE.
 *
 * So this *could* possibly be written with those
 * constraints in mind (relevant mostly if some
 * architecture has a slow bit-scan instruction)
 */
static inline int block_size_bits(unsigned int blocksize)
{
	return ilog2(blocksize);
}

static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
{
	BUG_ON(!PageLocked(page));

	if (!page_has_buffers(page))
		create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
	return page_buffers(page);
}

L
Linus Torvalds 已提交
1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671
/*
 * NOTE! All mapped/uptodate combinations are valid:
 *
 *	Mapped	Uptodate	Meaning
 *
 *	No	No		"unknown" - must do get_block()
 *	No	Yes		"hole" - zero-filled
 *	Yes	No		"allocated" - allocated on disk, not read in
 *	Yes	Yes		"valid" - allocated and up-to-date in memory.
 *
 * "Dirty" is valid only with the last case (mapped+uptodate).
 */

/*
 * While block_write_full_page is writing back the dirty buffers under
 * the page lock, whoever dirtied the buffers may decide to clean them
 * again at any time.  We handle that by only looking at the buffer
 * state inside lock_buffer().
 *
 * If block_write_full_page() is called for regular writeback
 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
 * locked buffer.   This only can happen if someone has written the buffer
 * directly, with submit_bh().  At the address_space level PageWriteback
 * prevents this contention from occurring.
1672 1673
 *
 * If block_write_full_page() is called with wbc->sync_mode ==
J
Jens Axboe 已提交
1674 1675
 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
 * causes the writes to be flagged as synchronous writes.
L
Linus Torvalds 已提交
1676 1677
 */
static int __block_write_full_page(struct inode *inode, struct page *page,
1678 1679
			get_block_t *get_block, struct writeback_control *wbc,
			bh_end_io_t *handler)
L
Linus Torvalds 已提交
1680 1681 1682 1683
{
	int err;
	sector_t block;
	sector_t last_block;
1684
	struct buffer_head *bh, *head;
1685
	unsigned int blocksize, bbits;
L
Linus Torvalds 已提交
1686
	int nr_underway = 0;
1687
	int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
J
Jens Axboe 已提交
1688
			WRITE_SYNC : WRITE);
L
Linus Torvalds 已提交
1689

1690
	head = create_page_buffers(page, inode,
L
Linus Torvalds 已提交
1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703
					(1 << BH_Dirty)|(1 << BH_Uptodate));

	/*
	 * Be very careful.  We have no exclusion from __set_page_dirty_buffers
	 * here, and the (potentially unmapped) buffers may become dirty at
	 * any time.  If a buffer becomes dirty here after we've inspected it
	 * then we just miss that fact, and the page stays dirty.
	 *
	 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
	 * handle that here by just cleaning them.
	 */

	bh = head;
1704 1705 1706 1707 1708
	blocksize = bh->b_size;
	bbits = block_size_bits(blocksize);

	block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
	last_block = (i_size_read(inode) - 1) >> bbits;
L
Linus Torvalds 已提交
1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725

	/*
	 * Get all the dirty buffers mapped to disk addresses and
	 * handle any aliases from the underlying blockdev's mapping.
	 */
	do {
		if (block > last_block) {
			/*
			 * mapped buffers outside i_size will occur, because
			 * this page can be outside i_size when there is a
			 * truncate in progress.
			 */
			/*
			 * The buffer was zeroed by block_write_full_page()
			 */
			clear_buffer_dirty(bh);
			set_buffer_uptodate(bh);
1726 1727
		} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
			   buffer_dirty(bh)) {
1728
			WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
1729 1730 1731
			err = get_block(inode, block, bh, 1);
			if (err)
				goto recover;
1732
			clear_buffer_delay(bh);
L
Linus Torvalds 已提交
1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749
			if (buffer_new(bh)) {
				/* blockdev mappings never come here */
				clear_buffer_new(bh);
				unmap_underlying_metadata(bh->b_bdev,
							bh->b_blocknr);
			}
		}
		bh = bh->b_this_page;
		block++;
	} while (bh != head);

	do {
		if (!buffer_mapped(bh))
			continue;
		/*
		 * If it's a fully non-blocking write attempt and we cannot
		 * lock the buffer then redirty the page.  Note that this can
1750 1751 1752
		 * potentially cause a busy-wait loop from writeback threads
		 * and kswapd activity, but those code paths have their own
		 * higher-level throttling.
L
Linus Torvalds 已提交
1753
		 */
1754
		if (wbc->sync_mode != WB_SYNC_NONE) {
L
Linus Torvalds 已提交
1755
			lock_buffer(bh);
N
Nick Piggin 已提交
1756
		} else if (!trylock_buffer(bh)) {
L
Linus Torvalds 已提交
1757 1758 1759 1760
			redirty_page_for_writepage(wbc, page);
			continue;
		}
		if (test_clear_buffer_dirty(bh)) {
1761
			mark_buffer_async_write_endio(bh, handler);
L
Linus Torvalds 已提交
1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776
		} else {
			unlock_buffer(bh);
		}
	} while ((bh = bh->b_this_page) != head);

	/*
	 * The page and its buffers are protected by PageWriteback(), so we can
	 * drop the bh refcounts early.
	 */
	BUG_ON(PageWriteback(page));
	set_page_writeback(page);

	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
1777
			submit_bh(write_op, bh);
L
Linus Torvalds 已提交
1778 1779 1780 1781
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1782
	unlock_page(page);
L
Linus Torvalds 已提交
1783 1784 1785 1786 1787 1788 1789 1790 1791 1792

	err = 0;
done:
	if (nr_underway == 0) {
		/*
		 * The page was marked dirty, but the buffers were
		 * clean.  Someone wrote them back by hand with
		 * ll_rw_block/submit_bh.  A rare case.
		 */
		end_page_writeback(page);
1793

L
Linus Torvalds 已提交
1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810
		/*
		 * The page and buffer_heads can be released at any time from
		 * here on.
		 */
	}
	return err;

recover:
	/*
	 * ENOSPC, or some other error.  We may already have added some
	 * blocks to the file, so we need to write these out to avoid
	 * exposing stale data.
	 * The page is currently locked and not marked for writeback
	 */
	bh = head;
	/* Recovery: lock and submit the mapped buffers */
	do {
1811 1812
		if (buffer_mapped(bh) && buffer_dirty(bh) &&
		    !buffer_delay(bh)) {
L
Linus Torvalds 已提交
1813
			lock_buffer(bh);
1814
			mark_buffer_async_write_endio(bh, handler);
L
Linus Torvalds 已提交
1815 1816 1817 1818 1819 1820 1821 1822 1823 1824
		} else {
			/*
			 * The buffer may have been set dirty during
			 * attachment to a dirty page.
			 */
			clear_buffer_dirty(bh);
		}
	} while ((bh = bh->b_this_page) != head);
	SetPageError(page);
	BUG_ON(PageWriteback(page));
1825
	mapping_set_error(page->mapping, err);
L
Linus Torvalds 已提交
1826 1827 1828 1829 1830
	set_page_writeback(page);
	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
			clear_buffer_dirty(bh);
1831
			submit_bh(write_op, bh);
L
Linus Torvalds 已提交
1832 1833 1834 1835
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1836
	unlock_page(page);
L
Linus Torvalds 已提交
1837 1838 1839
	goto done;
}

1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866
/*
 * If a page has any new buffers, zero them out here, and mark them uptodate
 * and dirty so they'll be written out (in order to prevent uninitialised
 * block data from leaking). And clear the new bit.
 */
void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
{
	unsigned int block_start, block_end;
	struct buffer_head *head, *bh;

	BUG_ON(!PageLocked(page));
	if (!page_has_buffers(page))
		return;

	bh = head = page_buffers(page);
	block_start = 0;
	do {
		block_end = block_start + bh->b_size;

		if (buffer_new(bh)) {
			if (block_end > from && block_start < to) {
				if (!PageUptodate(page)) {
					unsigned start, size;

					start = max(from, block_start);
					size = min(to, block_end) - start;

1867
					zero_user(page, start, size);
1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881
					set_buffer_uptodate(bh);
				}

				clear_buffer_new(bh);
				mark_buffer_dirty(bh);
			}
		}

		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);
}
EXPORT_SYMBOL(page_zero_new_buffers);

C
Christoph Hellwig 已提交
1882
int __block_write_begin(struct page *page, loff_t pos, unsigned len,
1883
		get_block_t *get_block)
L
Linus Torvalds 已提交
1884
{
C
Christoph Hellwig 已提交
1885 1886
	unsigned from = pos & (PAGE_CACHE_SIZE - 1);
	unsigned to = from + len;
1887
	struct inode *inode = page->mapping->host;
L
Linus Torvalds 已提交
1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898
	unsigned block_start, block_end;
	sector_t block;
	int err = 0;
	unsigned blocksize, bbits;
	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;

	BUG_ON(!PageLocked(page));
	BUG_ON(from > PAGE_CACHE_SIZE);
	BUG_ON(to > PAGE_CACHE_SIZE);
	BUG_ON(from > to);

1899 1900 1901
	head = create_page_buffers(page, inode, 0);
	blocksize = head->b_size;
	bbits = block_size_bits(blocksize);
L
Linus Torvalds 已提交
1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917

	block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);

	for(bh = head, block_start = 0; bh != head || !block_start;
	    block++, block_start=block_end, bh = bh->b_this_page) {
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (PageUptodate(page)) {
				if (!buffer_uptodate(bh))
					set_buffer_uptodate(bh);
			}
			continue;
		}
		if (buffer_new(bh))
			clear_buffer_new(bh);
		if (!buffer_mapped(bh)) {
1918
			WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
1919 1920
			err = get_block(inode, block, bh, 1);
			if (err)
1921
				break;
L
Linus Torvalds 已提交
1922 1923 1924 1925
			if (buffer_new(bh)) {
				unmap_underlying_metadata(bh->b_bdev,
							bh->b_blocknr);
				if (PageUptodate(page)) {
N
Nick Piggin 已提交
1926
					clear_buffer_new(bh);
L
Linus Torvalds 已提交
1927
					set_buffer_uptodate(bh);
N
Nick Piggin 已提交
1928
					mark_buffer_dirty(bh);
L
Linus Torvalds 已提交
1929 1930
					continue;
				}
1931 1932 1933 1934
				if (block_end > to || block_start < from)
					zero_user_segments(page,
						to, block_end,
						block_start, from);
L
Linus Torvalds 已提交
1935 1936 1937 1938 1939 1940 1941 1942 1943
				continue;
			}
		}
		if (PageUptodate(page)) {
			if (!buffer_uptodate(bh))
				set_buffer_uptodate(bh);
			continue; 
		}
		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1944
		    !buffer_unwritten(bh) &&
L
Linus Torvalds 已提交
1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955
		     (block_start < from || block_end > to)) {
			ll_rw_block(READ, 1, &bh);
			*wait_bh++=bh;
		}
	}
	/*
	 * If we issued read requests - let them complete.
	 */
	while(wait_bh > wait) {
		wait_on_buffer(*--wait_bh);
		if (!buffer_uptodate(*wait_bh))
1956
			err = -EIO;
L
Linus Torvalds 已提交
1957
	}
1958
	if (unlikely(err))
1959
		page_zero_new_buffers(page, from, to);
L
Linus Torvalds 已提交
1960 1961
	return err;
}
C
Christoph Hellwig 已提交
1962
EXPORT_SYMBOL(__block_write_begin);
L
Linus Torvalds 已提交
1963 1964 1965 1966 1967 1968 1969 1970 1971

static int __block_commit_write(struct inode *inode, struct page *page,
		unsigned from, unsigned to)
{
	unsigned block_start, block_end;
	int partial = 0;
	unsigned blocksize;
	struct buffer_head *bh, *head;

1972 1973
	bh = head = page_buffers(page);
	blocksize = bh->b_size;
L
Linus Torvalds 已提交
1974

1975 1976
	block_start = 0;
	do {
L
Linus Torvalds 已提交
1977 1978 1979 1980 1981 1982 1983 1984
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (!buffer_uptodate(bh))
				partial = 1;
		} else {
			set_buffer_uptodate(bh);
			mark_buffer_dirty(bh);
		}
1985
		clear_buffer_new(bh);
1986 1987 1988 1989

		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);
L
Linus Torvalds 已提交
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

	/*
	 * If this is a partial write which happened to make all buffers
	 * uptodate then we can optimize away a bogus readpage() for
	 * the next read(). Here we 'discover' whether the page went
	 * uptodate as a result of this (potentially partial) write.
	 */
	if (!partial)
		SetPageUptodate(page);
	return 0;
}

2002
/*
2003 2004 2005
 * block_write_begin takes care of the basic task of block allocation and
 * bringing partial write blocks uptodate first.
 *
2006
 * The filesystem needs to handle block truncation upon failure.
2007
 */
2008 2009
int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
		unsigned flags, struct page **pagep, get_block_t *get_block)
2010
{
2011
	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
2012
	struct page *page;
2013
	int status;
2014

2015 2016 2017
	page = grab_cache_page_write_begin(mapping, index, flags);
	if (!page)
		return -ENOMEM;
2018

2019
	status = __block_write_begin(page, pos, len, get_block);
2020
	if (unlikely(status)) {
2021 2022 2023
		unlock_page(page);
		page_cache_release(page);
		page = NULL;
2024 2025
	}

2026
	*pagep = page;
2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071
	return status;
}
EXPORT_SYMBOL(block_write_begin);

int block_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	struct inode *inode = mapping->host;
	unsigned start;

	start = pos & (PAGE_CACHE_SIZE - 1);

	if (unlikely(copied < len)) {
		/*
		 * The buffers that were written will now be uptodate, so we
		 * don't have to worry about a readpage reading them and
		 * overwriting a partial write. However if we have encountered
		 * a short write and only partially written into a buffer, it
		 * will not be marked uptodate, so a readpage might come in and
		 * destroy our partial write.
		 *
		 * Do the simplest thing, and just treat any short write to a
		 * non uptodate page as a zero-length write, and force the
		 * caller to redo the whole thing.
		 */
		if (!PageUptodate(page))
			copied = 0;

		page_zero_new_buffers(page, start+copied, start+len);
	}
	flush_dcache_page(page);

	/* This could be a short (even 0-length) commit */
	__block_commit_write(inode, page, start, start+copied);

	return copied;
}
EXPORT_SYMBOL(block_write_end);

int generic_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	struct inode *inode = mapping->host;
2072
	loff_t old_size = inode->i_size;
2073
	int i_size_changed = 0;
2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085

	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);

	/*
	 * No need to use i_size_read() here, the i_size
	 * cannot change under us because we hold i_mutex.
	 *
	 * But it's important to update i_size while still holding page lock:
	 * page writeout could otherwise come in and zero beyond i_size.
	 */
	if (pos+copied > inode->i_size) {
		i_size_write(inode, pos+copied);
2086
		i_size_changed = 1;
2087 2088 2089 2090 2091
	}

	unlock_page(page);
	page_cache_release(page);

2092 2093
	if (old_size < pos)
		pagecache_isize_extended(inode, old_size, pos);
2094 2095 2096 2097 2098 2099 2100 2101 2102
	/*
	 * Don't mark the inode dirty under page lock. First, it unnecessarily
	 * makes the holding time of page lock longer. Second, it forces lock
	 * ordering of page lock and transaction start for journaling
	 * filesystems.
	 */
	if (i_size_changed)
		mark_inode_dirty(inode);

2103 2104 2105 2106
	return copied;
}
EXPORT_SYMBOL(generic_write_end);

2107 2108 2109 2110 2111 2112 2113
/*
 * block_is_partially_uptodate checks whether buffers within a page are
 * uptodate or not.
 *
 * Returns true if all buffers which correspond to a file portion
 * we want to read are uptodate.
 */
2114 2115
int block_is_partially_uptodate(struct page *page, unsigned long from,
					unsigned long count)
2116 2117 2118 2119 2120 2121 2122 2123 2124
{
	unsigned block_start, block_end, blocksize;
	unsigned to;
	struct buffer_head *bh, *head;
	int ret = 1;

	if (!page_has_buffers(page))
		return 0;

2125 2126
	head = page_buffers(page);
	blocksize = head->b_size;
2127
	to = min_t(unsigned, PAGE_CACHE_SIZE - from, count);
2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151
	to = from + to;
	if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
		return 0;

	bh = head;
	block_start = 0;
	do {
		block_end = block_start + blocksize;
		if (block_end > from && block_start < to) {
			if (!buffer_uptodate(bh)) {
				ret = 0;
				break;
			}
			if (block_end >= to)
				break;
		}
		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);

	return ret;
}
EXPORT_SYMBOL(block_is_partially_uptodate);

L
Linus Torvalds 已提交
2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163
/*
 * Generic "read page" function for block devices that have the normal
 * get_block functionality. This is most of the block device filesystems.
 * Reads the page asynchronously --- the unlock_buffer() and
 * set/clear_buffer_uptodate() functions propagate buffer state into the
 * page struct once IO has completed.
 */
int block_read_full_page(struct page *page, get_block_t *get_block)
{
	struct inode *inode = page->mapping->host;
	sector_t iblock, lblock;
	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2164
	unsigned int blocksize, bbits;
L
Linus Torvalds 已提交
2165 2166 2167
	int nr, i;
	int fully_mapped = 1;

2168 2169 2170
	head = create_page_buffers(page, inode, 0);
	blocksize = head->b_size;
	bbits = block_size_bits(blocksize);
L
Linus Torvalds 已提交
2171

2172 2173
	iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
	lblock = (i_size_read(inode)+blocksize-1) >> bbits;
L
Linus Torvalds 已提交
2174 2175 2176 2177 2178 2179 2180 2181 2182
	bh = head;
	nr = 0;
	i = 0;

	do {
		if (buffer_uptodate(bh))
			continue;

		if (!buffer_mapped(bh)) {
2183 2184
			int err = 0;

L
Linus Torvalds 已提交
2185 2186
			fully_mapped = 0;
			if (iblock < lblock) {
2187
				WARN_ON(bh->b_size != blocksize);
2188 2189
				err = get_block(inode, iblock, bh, 0);
				if (err)
L
Linus Torvalds 已提交
2190 2191 2192
					SetPageError(page);
			}
			if (!buffer_mapped(bh)) {
2193
				zero_user(page, i * blocksize, blocksize);
2194 2195
				if (!err)
					set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242
				continue;
			}
			/*
			 * get_block() might have updated the buffer
			 * synchronously
			 */
			if (buffer_uptodate(bh))
				continue;
		}
		arr[nr++] = bh;
	} while (i++, iblock++, (bh = bh->b_this_page) != head);

	if (fully_mapped)
		SetPageMappedToDisk(page);

	if (!nr) {
		/*
		 * All buffers are uptodate - we can set the page uptodate
		 * as well. But not if get_block() returned an error.
		 */
		if (!PageError(page))
			SetPageUptodate(page);
		unlock_page(page);
		return 0;
	}

	/* Stage two: lock the buffers */
	for (i = 0; i < nr; i++) {
		bh = arr[i];
		lock_buffer(bh);
		mark_buffer_async_read(bh);
	}

	/*
	 * Stage 3: start the IO.  Check for uptodateness
	 * inside the buffer lock in case another process reading
	 * the underlying blockdev brought it uptodate (the sct fix).
	 */
	for (i = 0; i < nr; i++) {
		bh = arr[i];
		if (buffer_uptodate(bh))
			end_buffer_async_read(bh, 1);
		else
			submit_bh(READ, bh);
	}
	return 0;
}
2243
EXPORT_SYMBOL(block_read_full_page);
L
Linus Torvalds 已提交
2244 2245

/* utility function for filesystems that need to do work on expanding
N
Nick Piggin 已提交
2246
 * truncates.  Uses filesystem pagecache writes to allow the filesystem to
L
Linus Torvalds 已提交
2247 2248
 * deal with the hole.  
 */
N
Nick Piggin 已提交
2249
int generic_cont_expand_simple(struct inode *inode, loff_t size)
L
Linus Torvalds 已提交
2250 2251 2252
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;
N
Nick Piggin 已提交
2253
	void *fsdata;
L
Linus Torvalds 已提交
2254 2255
	int err;

N
npiggin@suse.de 已提交
2256 2257
	err = inode_newsize_ok(inode, size);
	if (err)
L
Linus Torvalds 已提交
2258 2259
		goto out;

N
Nick Piggin 已提交
2260 2261 2262 2263
	err = pagecache_write_begin(NULL, mapping, size, 0,
				AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
				&page, &fsdata);
	if (err)
2264 2265
		goto out;

N
Nick Piggin 已提交
2266 2267
	err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
	BUG_ON(err > 0);
2268

L
Linus Torvalds 已提交
2269 2270 2271
out:
	return err;
}
2272
EXPORT_SYMBOL(generic_cont_expand_simple);
L
Linus Torvalds 已提交
2273

2274 2275
static int cont_expand_zero(struct file *file, struct address_space *mapping,
			    loff_t pos, loff_t *bytes)
L
Linus Torvalds 已提交
2276 2277 2278
{
	struct inode *inode = mapping->host;
	unsigned blocksize = 1 << inode->i_blkbits;
N
Nick Piggin 已提交
2279 2280 2281 2282 2283 2284
	struct page *page;
	void *fsdata;
	pgoff_t index, curidx;
	loff_t curpos;
	unsigned zerofrom, offset, len;
	int err = 0;
L
Linus Torvalds 已提交
2285

N
Nick Piggin 已提交
2286 2287 2288 2289 2290
	index = pos >> PAGE_CACHE_SHIFT;
	offset = pos & ~PAGE_CACHE_MASK;

	while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
		zerofrom = curpos & ~PAGE_CACHE_MASK;
L
Linus Torvalds 已提交
2291 2292 2293 2294
		if (zerofrom & (blocksize-1)) {
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
N
Nick Piggin 已提交
2295
		len = PAGE_CACHE_SIZE - zerofrom;
L
Linus Torvalds 已提交
2296

N
Nick Piggin 已提交
2297 2298 2299 2300 2301
		err = pagecache_write_begin(file, mapping, curpos, len,
						AOP_FLAG_UNINTERRUPTIBLE,
						&page, &fsdata);
		if (err)
			goto out;
2302
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2303 2304 2305 2306 2307 2308
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
2309 2310

		balance_dirty_pages_ratelimited(mapping);
2311 2312 2313 2314 2315

		if (unlikely(fatal_signal_pending(current))) {
			err = -EINTR;
			goto out;
		}
N
Nick Piggin 已提交
2316
	}
L
Linus Torvalds 已提交
2317

N
Nick Piggin 已提交
2318 2319 2320
	/* page covers the boundary, find the boundary offset */
	if (index == curidx) {
		zerofrom = curpos & ~PAGE_CACHE_MASK;
L
Linus Torvalds 已提交
2321
		/* if we will expand the thing last block will be filled */
N
Nick Piggin 已提交
2322 2323 2324 2325
		if (offset <= zerofrom) {
			goto out;
		}
		if (zerofrom & (blocksize-1)) {
L
Linus Torvalds 已提交
2326 2327 2328
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
N
Nick Piggin 已提交
2329
		len = offset - zerofrom;
L
Linus Torvalds 已提交
2330

N
Nick Piggin 已提交
2331 2332 2333 2334 2335
		err = pagecache_write_begin(file, mapping, curpos, len,
						AOP_FLAG_UNINTERRUPTIBLE,
						&page, &fsdata);
		if (err)
			goto out;
2336
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2337 2338 2339 2340 2341 2342
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
L
Linus Torvalds 已提交
2343
	}
N
Nick Piggin 已提交
2344 2345 2346 2347 2348 2349 2350 2351
out:
	return err;
}

/*
 * For moronic filesystems that do not allow holes in file.
 * We may have to extend the file.
 */
2352
int cont_write_begin(struct file *file, struct address_space *mapping,
N
Nick Piggin 已提交
2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
			get_block_t *get_block, loff_t *bytes)
{
	struct inode *inode = mapping->host;
	unsigned blocksize = 1 << inode->i_blkbits;
	unsigned zerofrom;
	int err;

	err = cont_expand_zero(file, mapping, pos, bytes);
	if (err)
2364
		return err;
N
Nick Piggin 已提交
2365 2366 2367 2368 2369

	zerofrom = *bytes & ~PAGE_CACHE_MASK;
	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
		*bytes |= (blocksize-1);
		(*bytes)++;
L
Linus Torvalds 已提交
2370 2371
	}

2372
	return block_write_begin(mapping, pos, len, flags, pagep, get_block);
L
Linus Torvalds 已提交
2373
}
2374
EXPORT_SYMBOL(cont_write_begin);
L
Linus Torvalds 已提交
2375 2376 2377 2378 2379 2380 2381

int block_commit_write(struct page *page, unsigned from, unsigned to)
{
	struct inode *inode = page->mapping->host;
	__block_commit_write(inode,page,from,to);
	return 0;
}
2382
EXPORT_SYMBOL(block_commit_write);
L
Linus Torvalds 已提交
2383

2384 2385 2386 2387 2388 2389 2390 2391 2392 2393
/*
 * block_page_mkwrite() is not allowed to change the file size as it gets
 * called from a page fault handler when a page is first dirtied. Hence we must
 * be careful to check for EOF conditions here. We set the page up correctly
 * for a written page which means we get ENOSPC checking when writing into
 * holes and correct delalloc and unwritten extent mapping on filesystems that
 * support these features.
 *
 * We are not allowed to take the i_mutex here so we have to play games to
 * protect against truncate races as the page could now be beyond EOF.  Because
2394
 * truncate writes the inode size before removing pages, once we have the
2395 2396 2397
 * page lock we can determine safely if the page is beyond EOF. If it is not
 * beyond EOF, then the page is guaranteed safe against truncation until we
 * unlock the page.
2398
 *
2399 2400
 * Direct callers of this function should protect against filesystem freezing
 * using sb_start_write() - sb_end_write() functions.
2401
 */
2402 2403
int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
			 get_block_t get_block)
2404
{
2405
	struct page *page = vmf->page;
A
Al Viro 已提交
2406
	struct inode *inode = file_inode(vma->vm_file);
2407 2408
	unsigned long end;
	loff_t size;
2409
	int ret;
2410 2411 2412 2413

	lock_page(page);
	size = i_size_read(inode);
	if ((page->mapping != inode->i_mapping) ||
N
Nick Piggin 已提交
2414
	    (page_offset(page) > size)) {
2415 2416 2417
		/* We overload EFAULT to mean page got truncated */
		ret = -EFAULT;
		goto out_unlock;
2418 2419 2420 2421 2422 2423 2424 2425
	}

	/* page is wholly or partially inside EOF */
	if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
		end = size & ~PAGE_CACHE_MASK;
	else
		end = PAGE_CACHE_SIZE;

C
Christoph Hellwig 已提交
2426
	ret = __block_write_begin(page, 0, end, get_block);
2427 2428 2429
	if (!ret)
		ret = block_commit_write(page, 0, end);

2430 2431
	if (unlikely(ret < 0))
		goto out_unlock;
2432
	set_page_dirty(page);
2433
	wait_for_stable_page(page);
2434 2435 2436
	return 0;
out_unlock:
	unlock_page(page);
2437
	return ret;
2438 2439 2440 2441 2442 2443
}
EXPORT_SYMBOL(__block_page_mkwrite);

int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
		   get_block_t get_block)
{
2444
	int ret;
A
Al Viro 已提交
2445
	struct super_block *sb = file_inode(vma->vm_file)->i_sb;
2446

2447
	sb_start_pagefault(sb);
2448 2449 2450 2451 2452 2453 2454

	/*
	 * Update file times before taking page lock. We may end up failing the
	 * fault so this update may be superfluous but who really cares...
	 */
	file_update_time(vma->vm_file);

2455
	ret = __block_page_mkwrite(vma, vmf, get_block);
2456
	sb_end_pagefault(sb);
2457
	return block_page_mkwrite_return(ret);
2458
}
2459
EXPORT_SYMBOL(block_page_mkwrite);
L
Linus Torvalds 已提交
2460 2461

/*
N
Nick Piggin 已提交
2462
 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
L
Linus Torvalds 已提交
2463 2464 2465 2466 2467
 * immediately, while under the page lock.  So it needs a special end_io
 * handler which does not touch the bh after unlocking it.
 */
static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
{
2468
	__end_buffer_read_notouch(bh, uptodate);
L
Linus Torvalds 已提交
2469 2470
}

N
Nick Piggin 已提交
2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494
/*
 * Attach the singly-linked list of buffers created by nobh_write_begin, to
 * the page (converting it to circular linked list and taking care of page
 * dirty races).
 */
static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
{
	struct buffer_head *bh;

	BUG_ON(!PageLocked(page));

	spin_lock(&page->mapping->private_lock);
	bh = head;
	do {
		if (PageDirty(page))
			set_buffer_dirty(bh);
		if (!bh->b_this_page)
			bh->b_this_page = head;
		bh = bh->b_this_page;
	} while (bh != head);
	attach_page_buffers(page, head);
	spin_unlock(&page->mapping->private_lock);
}

L
Linus Torvalds 已提交
2495
/*
2496 2497
 * On entry, the page is fully not uptodate.
 * On exit the page is fully uptodate in the areas outside (from,to)
2498
 * The filesystem needs to handle block truncation upon failure.
L
Linus Torvalds 已提交
2499
 */
2500
int nobh_write_begin(struct address_space *mapping,
N
Nick Piggin 已提交
2501 2502
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
L
Linus Torvalds 已提交
2503 2504
			get_block_t *get_block)
{
N
Nick Piggin 已提交
2505
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2506 2507
	const unsigned blkbits = inode->i_blkbits;
	const unsigned blocksize = 1 << blkbits;
N
Nick Piggin 已提交
2508
	struct buffer_head *head, *bh;
N
Nick Piggin 已提交
2509 2510 2511
	struct page *page;
	pgoff_t index;
	unsigned from, to;
L
Linus Torvalds 已提交
2512
	unsigned block_in_page;
N
Nick Piggin 已提交
2513
	unsigned block_start, block_end;
L
Linus Torvalds 已提交
2514 2515 2516 2517 2518
	sector_t block_in_file;
	int nr_reads = 0;
	int ret = 0;
	int is_mapped_to_disk = 1;

N
Nick Piggin 已提交
2519 2520 2521 2522
	index = pos >> PAGE_CACHE_SHIFT;
	from = pos & (PAGE_CACHE_SIZE - 1);
	to = from + len;

2523
	page = grab_cache_page_write_begin(mapping, index, flags);
N
Nick Piggin 已提交
2524 2525 2526 2527 2528 2529
	if (!page)
		return -ENOMEM;
	*pagep = page;
	*fsdata = NULL;

	if (page_has_buffers(page)) {
2530 2531 2532 2533
		ret = __block_write_begin(page, pos, len, get_block);
		if (unlikely(ret))
			goto out_release;
		return ret;
N
Nick Piggin 已提交
2534
	}
N
Nick Piggin 已提交
2535

L
Linus Torvalds 已提交
2536 2537 2538
	if (PageMappedToDisk(page))
		return 0;

N
Nick Piggin 已提交
2539 2540 2541 2542 2543 2544 2545 2546 2547 2548
	/*
	 * Allocate buffers so that we can keep track of state, and potentially
	 * attach them to the page if an error occurs. In the common case of
	 * no error, they will just be freed again without ever being attached
	 * to the page (which is all OK, because we're under the page lock).
	 *
	 * Be careful: the buffer linked list is a NULL terminated one, rather
	 * than the circular one we're used to.
	 */
	head = alloc_page_buffers(page, blocksize, 0);
N
Nick Piggin 已提交
2549 2550 2551 2552
	if (!head) {
		ret = -ENOMEM;
		goto out_release;
	}
N
Nick Piggin 已提交
2553

L
Linus Torvalds 已提交
2554 2555 2556 2557 2558 2559 2560
	block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);

	/*
	 * We loop across all blocks in the page, whether or not they are
	 * part of the affected region.  This is so we can discover if the
	 * page is fully mapped-to-disk.
	 */
N
Nick Piggin 已提交
2561
	for (block_start = 0, block_in_page = 0, bh = head;
L
Linus Torvalds 已提交
2562
		  block_start < PAGE_CACHE_SIZE;
N
Nick Piggin 已提交
2563
		  block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2564 2565
		int create;

N
Nick Piggin 已提交
2566 2567
		block_end = block_start + blocksize;
		bh->b_state = 0;
L
Linus Torvalds 已提交
2568 2569 2570 2571
		create = 1;
		if (block_start >= to)
			create = 0;
		ret = get_block(inode, block_in_file + block_in_page,
N
Nick Piggin 已提交
2572
					bh, create);
L
Linus Torvalds 已提交
2573 2574
		if (ret)
			goto failed;
N
Nick Piggin 已提交
2575
		if (!buffer_mapped(bh))
L
Linus Torvalds 已提交
2576
			is_mapped_to_disk = 0;
N
Nick Piggin 已提交
2577 2578 2579 2580
		if (buffer_new(bh))
			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
		if (PageUptodate(page)) {
			set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2581
			continue;
N
Nick Piggin 已提交
2582 2583
		}
		if (buffer_new(bh) || !buffer_mapped(bh)) {
2584 2585
			zero_user_segments(page, block_start, from,
							to, block_end);
L
Linus Torvalds 已提交
2586 2587
			continue;
		}
N
Nick Piggin 已提交
2588
		if (buffer_uptodate(bh))
L
Linus Torvalds 已提交
2589 2590
			continue;	/* reiserfs does this */
		if (block_start < from || block_end > to) {
N
Nick Piggin 已提交
2591 2592 2593 2594
			lock_buffer(bh);
			bh->b_end_io = end_buffer_read_nobh;
			submit_bh(READ, bh);
			nr_reads++;
L
Linus Torvalds 已提交
2595 2596 2597 2598 2599 2600 2601 2602 2603
		}
	}

	if (nr_reads) {
		/*
		 * The page is locked, so these buffers are protected from
		 * any VM or truncate activity.  Hence we don't need to care
		 * for the buffer_head refcounts.
		 */
N
Nick Piggin 已提交
2604
		for (bh = head; bh; bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615
			wait_on_buffer(bh);
			if (!buffer_uptodate(bh))
				ret = -EIO;
		}
		if (ret)
			goto failed;
	}

	if (is_mapped_to_disk)
		SetPageMappedToDisk(page);

N
Nick Piggin 已提交
2616
	*fsdata = head; /* to be released by nobh_write_end */
N
Nick Piggin 已提交
2617

L
Linus Torvalds 已提交
2618 2619 2620
	return 0;

failed:
N
Nick Piggin 已提交
2621
	BUG_ON(!ret);
L
Linus Torvalds 已提交
2622
	/*
N
Nick Piggin 已提交
2623 2624 2625 2626 2627
	 * Error recovery is a bit difficult. We need to zero out blocks that
	 * were newly allocated, and dirty them to ensure they get written out.
	 * Buffers need to be attached to the page at this point, otherwise
	 * the handling of potential IO errors during writeout would be hard
	 * (could try doing synchronous writeout, but what if that fails too?)
L
Linus Torvalds 已提交
2628
	 */
N
Nick Piggin 已提交
2629 2630
	attach_nobh_buffers(page, head);
	page_zero_new_buffers(page, from, to);
N
Nick Piggin 已提交
2631

N
Nick Piggin 已提交
2632 2633 2634 2635
out_release:
	unlock_page(page);
	page_cache_release(page);
	*pagep = NULL;
N
Nick Piggin 已提交
2636

2637 2638
	return ret;
}
N
Nick Piggin 已提交
2639
EXPORT_SYMBOL(nobh_write_begin);
L
Linus Torvalds 已提交
2640

N
Nick Piggin 已提交
2641 2642 2643
int nobh_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
L
Linus Torvalds 已提交
2644 2645
{
	struct inode *inode = page->mapping->host;
N
Nick Piggin 已提交
2646
	struct buffer_head *head = fsdata;
N
Nick Piggin 已提交
2647
	struct buffer_head *bh;
2648
	BUG_ON(fsdata != NULL && page_has_buffers(page));
L
Linus Torvalds 已提交
2649

2650
	if (unlikely(copied < len) && head)
2651 2652 2653 2654
		attach_nobh_buffers(page, head);
	if (page_has_buffers(page))
		return generic_write_end(file, mapping, pos, len,
					copied, page, fsdata);
N
Nick Piggin 已提交
2655

N
Nick Piggin 已提交
2656
	SetPageUptodate(page);
L
Linus Torvalds 已提交
2657
	set_page_dirty(page);
N
Nick Piggin 已提交
2658 2659
	if (pos+copied > inode->i_size) {
		i_size_write(inode, pos+copied);
L
Linus Torvalds 已提交
2660 2661
		mark_inode_dirty(inode);
	}
N
Nick Piggin 已提交
2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672

	unlock_page(page);
	page_cache_release(page);

	while (head) {
		bh = head;
		head = head->b_this_page;
		free_buffer_head(bh);
	}

	return copied;
L
Linus Torvalds 已提交
2673
}
N
Nick Piggin 已提交
2674
EXPORT_SYMBOL(nobh_write_end);
L
Linus Torvalds 已提交
2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717

/*
 * nobh_writepage() - based on block_full_write_page() except
 * that it tries to operate without attaching bufferheads to
 * the page.
 */
int nobh_writepage(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
	unsigned offset;
	int ret;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
		goto out;

	/* Is the page fully outside i_size? (truncate in progress) */
	offset = i_size & (PAGE_CACHE_SIZE-1);
	if (page->index >= end_index+1 || !offset) {
		/*
		 * The page may have dirty, unmapped buffers.  For example,
		 * they may have been added in ext3_writepage().  Make them
		 * freeable here, so the page does not leak.
		 */
#if 0
		/* Not really sure about this  - do we need this ? */
		if (page->mapping->a_ops->invalidatepage)
			page->mapping->a_ops->invalidatepage(page, offset);
#endif
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
	 * writepage invocation because it may be mmapped.  "A file is mapped
	 * in multiples of the page size.  For a file that is not a multiple of
	 * the  page size, the remaining memory is zeroed when mapped, and
	 * writes to that region are not written out to the file."
	 */
2718
	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
L
Linus Torvalds 已提交
2719 2720 2721
out:
	ret = mpage_writepage(page, get_block, wbc);
	if (ret == -EAGAIN)
2722 2723
		ret = __block_write_full_page(inode, page, get_block, wbc,
					      end_buffer_async_write);
L
Linus Torvalds 已提交
2724 2725 2726 2727
	return ret;
}
EXPORT_SYMBOL(nobh_writepage);

N
Nick Piggin 已提交
2728 2729
int nobh_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
L
Linus Torvalds 已提交
2730 2731 2732
{
	pgoff_t index = from >> PAGE_CACHE_SHIFT;
	unsigned offset = from & (PAGE_CACHE_SIZE-1);
N
Nick Piggin 已提交
2733 2734 2735 2736
	unsigned blocksize;
	sector_t iblock;
	unsigned length, pos;
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2737
	struct page *page;
N
Nick Piggin 已提交
2738 2739
	struct buffer_head map_bh;
	int err;
L
Linus Torvalds 已提交
2740

N
Nick Piggin 已提交
2741 2742 2743 2744 2745 2746 2747 2748 2749
	blocksize = 1 << inode->i_blkbits;
	length = offset & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;

	length = blocksize - length;
	iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2750 2751

	page = grab_cache_page(mapping, index);
N
Nick Piggin 已提交
2752
	err = -ENOMEM;
L
Linus Torvalds 已提交
2753 2754 2755
	if (!page)
		goto out;

N
Nick Piggin 已提交
2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769
	if (page_has_buffers(page)) {
has_buffers:
		unlock_page(page);
		page_cache_release(page);
		return block_truncate_page(mapping, from, get_block);
	}

	/* Find the buffer that contains "offset" */
	pos = blocksize;
	while (offset >= pos) {
		iblock++;
		pos += blocksize;
	}

2770 2771
	map_bh.b_size = blocksize;
	map_bh.b_state = 0;
N
Nick Piggin 已提交
2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792
	err = get_block(inode, iblock, &map_bh, 0);
	if (err)
		goto unlock;
	/* unmapped? It's a hole - nothing to do */
	if (!buffer_mapped(&map_bh))
		goto unlock;

	/* Ok, it's mapped. Make sure it's up-to-date */
	if (!PageUptodate(page)) {
		err = mapping->a_ops->readpage(NULL, page);
		if (err) {
			page_cache_release(page);
			goto out;
		}
		lock_page(page);
		if (!PageUptodate(page)) {
			err = -EIO;
			goto unlock;
		}
		if (page_has_buffers(page))
			goto has_buffers;
L
Linus Torvalds 已提交
2793
	}
2794
	zero_user(page, offset, length);
N
Nick Piggin 已提交
2795 2796 2797 2798
	set_page_dirty(page);
	err = 0;

unlock:
L
Linus Torvalds 已提交
2799 2800 2801
	unlock_page(page);
	page_cache_release(page);
out:
N
Nick Piggin 已提交
2802
	return err;
L
Linus Torvalds 已提交
2803 2804 2805 2806 2807 2808 2809 2810 2811
}
EXPORT_SYMBOL(nobh_truncate_page);

int block_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
{
	pgoff_t index = from >> PAGE_CACHE_SHIFT;
	unsigned offset = from & (PAGE_CACHE_SIZE-1);
	unsigned blocksize;
2812
	sector_t iblock;
L
Linus Torvalds 已提交
2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826
	unsigned length, pos;
	struct inode *inode = mapping->host;
	struct page *page;
	struct buffer_head *bh;
	int err;

	blocksize = 1 << inode->i_blkbits;
	length = offset & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;

	length = blocksize - length;
2827
	iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847
	
	page = grab_cache_page(mapping, index);
	err = -ENOMEM;
	if (!page)
		goto out;

	if (!page_has_buffers(page))
		create_empty_buffers(page, blocksize, 0);

	/* Find the buffer that contains "offset" */
	bh = page_buffers(page);
	pos = blocksize;
	while (offset >= pos) {
		bh = bh->b_this_page;
		iblock++;
		pos += blocksize;
	}

	err = 0;
	if (!buffer_mapped(bh)) {
2848
		WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860
		err = get_block(inode, iblock, bh, 0);
		if (err)
			goto unlock;
		/* unmapped? It's a hole - nothing to do */
		if (!buffer_mapped(bh))
			goto unlock;
	}

	/* Ok, it's mapped. Make sure it's up-to-date */
	if (PageUptodate(page))
		set_buffer_uptodate(bh);

2861
	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
L
Linus Torvalds 已提交
2862 2863 2864 2865 2866 2867 2868 2869
		err = -EIO;
		ll_rw_block(READ, 1, &bh);
		wait_on_buffer(bh);
		/* Uhhuh. Read error. Complain and punt. */
		if (!buffer_uptodate(bh))
			goto unlock;
	}

2870
	zero_user(page, offset, length);
L
Linus Torvalds 已提交
2871 2872 2873 2874 2875 2876 2877 2878 2879
	mark_buffer_dirty(bh);
	err = 0;

unlock:
	unlock_page(page);
	page_cache_release(page);
out:
	return err;
}
2880
EXPORT_SYMBOL(block_truncate_page);
L
Linus Torvalds 已提交
2881 2882 2883 2884

/*
 * The generic ->writepage function for buffer-backed address_spaces
 */
2885 2886
int block_write_full_page(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
L
Linus Torvalds 已提交
2887 2888 2889 2890 2891 2892 2893 2894
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
	unsigned offset;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
2895
		return __block_write_full_page(inode, page, get_block, wbc,
2896
					       end_buffer_async_write);
L
Linus Torvalds 已提交
2897 2898 2899 2900 2901 2902 2903 2904 2905

	/* Is the page fully outside i_size? (truncate in progress) */
	offset = i_size & (PAGE_CACHE_SIZE-1);
	if (page->index >= end_index+1 || !offset) {
		/*
		 * The page may have dirty, unmapped buffers.  For example,
		 * they may have been added in ext3_writepage().  Make them
		 * freeable here, so the page does not leak.
		 */
2906
		do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
L
Linus Torvalds 已提交
2907 2908 2909 2910 2911 2912
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
2913
	 * writepage invocation because it may be mmapped.  "A file is mapped
L
Linus Torvalds 已提交
2914 2915 2916 2917
	 * in multiples of the page size.  For a file that is not a multiple of
	 * the  page size, the remaining memory is zeroed when mapped, and
	 * writes to that region are not written out to the file."
	 */
2918
	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2919 2920
	return __block_write_full_page(inode, page, get_block, wbc,
							end_buffer_async_write);
2921
}
2922
EXPORT_SYMBOL(block_write_full_page);
2923

L
Linus Torvalds 已提交
2924 2925 2926 2927 2928 2929 2930
sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
			    get_block_t *get_block)
{
	struct buffer_head tmp;
	struct inode *inode = mapping->host;
	tmp.b_state = 0;
	tmp.b_blocknr = 0;
2931
	tmp.b_size = 1 << inode->i_blkbits;
L
Linus Torvalds 已提交
2932 2933 2934
	get_block(inode, block, &tmp, 0);
	return tmp.b_blocknr;
}
2935
EXPORT_SYMBOL(generic_block_bmap);
L
Linus Torvalds 已提交
2936

2937
static void end_bio_bh_io_sync(struct bio *bio, int err)
L
Linus Torvalds 已提交
2938 2939 2940
{
	struct buffer_head *bh = bio->bi_private;

2941 2942 2943
	if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
		set_bit(BH_Quiet, &bh->b_state);

L
Linus Torvalds 已提交
2944 2945 2946 2947
	bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
	bio_put(bio);
}

2948 2949
/*
 * This allows us to do IO even on the odd last sectors
2950
 * of a device, even if the block size is some multiple
2951 2952 2953 2954 2955 2956 2957 2958 2959
 * of the physical sector size.
 *
 * We'll just truncate the bio to the size of the device,
 * and clear the end of the buffer head manually.
 *
 * Truly out-of-range accesses will turn into actual IO
 * errors, this only handles the "we need to be able to
 * do IO at the final sector" case.
 */
2960
void guard_bio_eod(int rw, struct bio *bio)
2961 2962
{
	sector_t maxsector;
2963 2964
	struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
	unsigned truncated_bytes;
2965 2966 2967 2968 2969 2970 2971 2972 2973 2974

	maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
	if (!maxsector)
		return;

	/*
	 * If the *whole* IO is past the end of the device,
	 * let it through, and the IO layer will turn it into
	 * an EIO.
	 */
2975
	if (unlikely(bio->bi_iter.bi_sector >= maxsector))
2976 2977
		return;

2978
	maxsector -= bio->bi_iter.bi_sector;
2979
	if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
2980 2981
		return;

2982 2983
	/* Uhhuh. We've got a bio that straddles the device size! */
	truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
2984 2985

	/* Truncate the bio.. */
2986 2987
	bio->bi_iter.bi_size -= truncated_bytes;
	bvec->bv_len -= truncated_bytes;
2988 2989

	/* ..and clear the end of the buffer for reads */
2990
	if ((rw & RW_MASK) == READ) {
2991 2992
		zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
				truncated_bytes);
2993 2994 2995
	}
}

2996
int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
L
Linus Torvalds 已提交
2997 2998 2999 3000 3001 3002 3003
{
	struct bio *bio;
	int ret = 0;

	BUG_ON(!buffer_locked(bh));
	BUG_ON(!buffer_mapped(bh));
	BUG_ON(!bh->b_end_io);
3004 3005
	BUG_ON(buffer_delay(bh));
	BUG_ON(buffer_unwritten(bh));
L
Linus Torvalds 已提交
3006 3007

	/*
3008
	 * Only clear out a write error when rewriting
L
Linus Torvalds 已提交
3009
	 */
3010
	if (test_set_buffer_req(bh) && (rw & WRITE))
L
Linus Torvalds 已提交
3011 3012 3013 3014 3015 3016 3017 3018
		clear_buffer_write_io_error(bh);

	/*
	 * from here on down, it's all bio -- do the initial mapping,
	 * submit_bio -> generic_make_request may further map this bio around
	 */
	bio = bio_alloc(GFP_NOIO, 1);

3019
	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
L
Linus Torvalds 已提交
3020 3021 3022 3023 3024 3025
	bio->bi_bdev = bh->b_bdev;
	bio->bi_io_vec[0].bv_page = bh->b_page;
	bio->bi_io_vec[0].bv_len = bh->b_size;
	bio->bi_io_vec[0].bv_offset = bh_offset(bh);

	bio->bi_vcnt = 1;
3026
	bio->bi_iter.bi_size = bh->b_size;
L
Linus Torvalds 已提交
3027 3028 3029

	bio->bi_end_io = end_bio_bh_io_sync;
	bio->bi_private = bh;
3030
	bio->bi_flags |= bio_flags;
L
Linus Torvalds 已提交
3031

3032
	/* Take care of bh's that straddle the end of the device */
3033
	guard_bio_eod(rw, bio);
3034

3035 3036 3037 3038 3039
	if (buffer_meta(bh))
		rw |= REQ_META;
	if (buffer_prio(bh))
		rw |= REQ_PRIO;

L
Linus Torvalds 已提交
3040 3041 3042
	submit_bio(rw, bio);
	return ret;
}
3043 3044 3045 3046 3047 3048
EXPORT_SYMBOL_GPL(_submit_bh);

int submit_bh(int rw, struct buffer_head *bh)
{
	return _submit_bh(rw, bh, 0);
}
3049
EXPORT_SYMBOL(submit_bh);
L
Linus Torvalds 已提交
3050 3051 3052

/**
 * ll_rw_block: low-level access to block devices (DEPRECATED)
C
Christoph Hellwig 已提交
3053
 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
L
Linus Torvalds 已提交
3054 3055 3056
 * @nr: number of &struct buffer_heads in the array
 * @bhs: array of pointers to &struct buffer_head
 *
3057 3058
 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
 * requests an I/O operation on them, either a %READ or a %WRITE.  The third
C
Christoph Hellwig 已提交
3059 3060
 * %READA option is described in the documentation for generic_make_request()
 * which ll_rw_block() calls.
L
Linus Torvalds 已提交
3061 3062
 *
 * This function drops any buffer that it cannot get a lock on (with the
C
Christoph Hellwig 已提交
3063 3064 3065 3066 3067
 * BH_Lock state bit), any buffer that appears to be clean when doing a write
 * request, and any buffer that appears to be up-to-date when doing read
 * request.  Further it marks as clean buffers that are processed for
 * writing (the buffer cache won't assume that they are actually clean
 * until the buffer gets unlocked).
L
Linus Torvalds 已提交
3068 3069
 *
 * ll_rw_block sets b_end_io to simple completion handler that marks
3070
 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
L
Linus Torvalds 已提交
3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082
 * any waiters. 
 *
 * All of the buffers must be for the same device, and must also be a
 * multiple of the current approved size for the device.
 */
void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
{
	int i;

	for (i = 0; i < nr; i++) {
		struct buffer_head *bh = bhs[i];

C
Christoph Hellwig 已提交
3083
		if (!trylock_buffer(bh))
L
Linus Torvalds 已提交
3084
			continue;
C
Christoph Hellwig 已提交
3085
		if (rw == WRITE) {
L
Linus Torvalds 已提交
3086
			if (test_clear_buffer_dirty(bh)) {
3087
				bh->b_end_io = end_buffer_write_sync;
3088
				get_bh(bh);
C
Christoph Hellwig 已提交
3089
				submit_bh(WRITE, bh);
L
Linus Torvalds 已提交
3090 3091 3092 3093
				continue;
			}
		} else {
			if (!buffer_uptodate(bh)) {
3094
				bh->b_end_io = end_buffer_read_sync;
3095
				get_bh(bh);
L
Linus Torvalds 已提交
3096 3097 3098 3099 3100 3101 3102
				submit_bh(rw, bh);
				continue;
			}
		}
		unlock_buffer(bh);
	}
}
3103
EXPORT_SYMBOL(ll_rw_block);
L
Linus Torvalds 已提交
3104

C
Christoph Hellwig 已提交
3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117
void write_dirty_buffer(struct buffer_head *bh, int rw)
{
	lock_buffer(bh);
	if (!test_clear_buffer_dirty(bh)) {
		unlock_buffer(bh);
		return;
	}
	bh->b_end_io = end_buffer_write_sync;
	get_bh(bh);
	submit_bh(rw, bh);
}
EXPORT_SYMBOL(write_dirty_buffer);

L
Linus Torvalds 已提交
3118 3119 3120 3121 3122
/*
 * For a data-integrity writeout, we need to wait upon any in-progress I/O
 * and then start new I/O and then wait upon it.  The caller must have a ref on
 * the buffer_head.
 */
C
Christoph Hellwig 已提交
3123
int __sync_dirty_buffer(struct buffer_head *bh, int rw)
L
Linus Torvalds 已提交
3124 3125 3126 3127 3128 3129 3130 3131
{
	int ret = 0;

	WARN_ON(atomic_read(&bh->b_count) < 1);
	lock_buffer(bh);
	if (test_clear_buffer_dirty(bh)) {
		get_bh(bh);
		bh->b_end_io = end_buffer_write_sync;
C
Christoph Hellwig 已提交
3132
		ret = submit_bh(rw, bh);
L
Linus Torvalds 已提交
3133 3134 3135 3136 3137 3138 3139 3140
		wait_on_buffer(bh);
		if (!ret && !buffer_uptodate(bh))
			ret = -EIO;
	} else {
		unlock_buffer(bh);
	}
	return ret;
}
C
Christoph Hellwig 已提交
3141 3142 3143 3144 3145 3146
EXPORT_SYMBOL(__sync_dirty_buffer);

int sync_dirty_buffer(struct buffer_head *bh)
{
	return __sync_dirty_buffer(bh, WRITE_SYNC);
}
3147
EXPORT_SYMBOL(sync_dirty_buffer);
L
Linus Torvalds 已提交
3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182

/*
 * try_to_free_buffers() checks if all the buffers on this particular page
 * are unused, and releases them if so.
 *
 * Exclusion against try_to_free_buffers may be obtained by either
 * locking the page or by holding its mapping's private_lock.
 *
 * If the page is dirty but all the buffers are clean then we need to
 * be sure to mark the page clean as well.  This is because the page
 * may be against a block device, and a later reattachment of buffers
 * to a dirty page will set *all* buffers dirty.  Which would corrupt
 * filesystem data on the same device.
 *
 * The same applies to regular filesystem pages: if all the buffers are
 * clean then we set the page clean and proceed.  To do that, we require
 * total exclusion from __set_page_dirty_buffers().  That is obtained with
 * private_lock.
 *
 * try_to_free_buffers() is non-blocking.
 */
static inline int buffer_busy(struct buffer_head *bh)
{
	return atomic_read(&bh->b_count) |
		(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
}

static int
drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
{
	struct buffer_head *head = page_buffers(page);
	struct buffer_head *bh;

	bh = head;
	do {
A
akpm@osdl.org 已提交
3183
		if (buffer_write_io_error(bh) && page->mapping)
L
Linus Torvalds 已提交
3184 3185 3186 3187 3188 3189 3190 3191 3192
			set_bit(AS_EIO, &page->mapping->flags);
		if (buffer_busy(bh))
			goto failed;
		bh = bh->b_this_page;
	} while (bh != head);

	do {
		struct buffer_head *next = bh->b_this_page;

3193
		if (bh->b_assoc_map)
L
Linus Torvalds 已提交
3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210
			__remove_assoc_queue(bh);
		bh = next;
	} while (bh != head);
	*buffers_to_free = head;
	__clear_page_buffers(page);
	return 1;
failed:
	return 0;
}

int try_to_free_buffers(struct page *page)
{
	struct address_space * const mapping = page->mapping;
	struct buffer_head *buffers_to_free = NULL;
	int ret = 0;

	BUG_ON(!PageLocked(page));
3211
	if (PageWriteback(page))
L
Linus Torvalds 已提交
3212 3213 3214 3215 3216 3217 3218 3219 3220
		return 0;

	if (mapping == NULL) {		/* can this still happen? */
		ret = drop_buffers(page, &buffers_to_free);
		goto out;
	}

	spin_lock(&mapping->private_lock);
	ret = drop_buffers(page, &buffers_to_free);
3221 3222 3223 3224 3225 3226 3227 3228 3229 3230

	/*
	 * If the filesystem writes its buffers by hand (eg ext3)
	 * then we can have clean buffers against a dirty page.  We
	 * clean the page here; otherwise the VM will never notice
	 * that the filesystem did any IO at all.
	 *
	 * Also, during truncate, discard_buffer will have marked all
	 * the page's buffers clean.  We discover that here and clean
	 * the page also.
3231 3232 3233 3234
	 *
	 * private_lock must be held over this entire operation in order
	 * to synchronise against __set_page_dirty_buffers and prevent the
	 * dirty bit from being lost.
3235
	 */
3236 3237
	if (ret && TestClearPageDirty(page))
		account_page_cleaned(page, mapping);
3238
	spin_unlock(&mapping->private_lock);
L
Linus Torvalds 已提交
3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257
out:
	if (buffers_to_free) {
		struct buffer_head *bh = buffers_to_free;

		do {
			struct buffer_head *next = bh->b_this_page;
			free_buffer_head(bh);
			bh = next;
		} while (bh != buffers_to_free);
	}
	return ret;
}
EXPORT_SYMBOL(try_to_free_buffers);

/*
 * There are no bdflush tunables left.  But distributions are
 * still running obsolete flush daemons, so we terminate them here.
 *
 * Use of bdflush() is deprecated and will be removed in a future kernel.
3258
 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
L
Linus Torvalds 已提交
3259
 */
3260
SYSCALL_DEFINE2(bdflush, int, func, long, data)
L
Linus Torvalds 已提交
3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282
{
	static int msg_count;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (msg_count < 5) {
		msg_count++;
		printk(KERN_INFO
			"warning: process `%s' used the obsolete bdflush"
			" system call\n", current->comm);
		printk(KERN_INFO "Fix your initscripts?\n");
	}

	if (func == 1)
		do_exit(0);
	return 0;
}

/*
 * Buffer-head allocation
 */
3283
static struct kmem_cache *bh_cachep __read_mostly;
L
Linus Torvalds 已提交
3284 3285 3286 3287 3288

/*
 * Once the number of bh's in the machine exceeds this level, we start
 * stripping them in writeback.
 */
3289
static unsigned long max_buffer_heads;
L
Linus Torvalds 已提交
3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304

int buffer_heads_over_limit;

struct bh_accounting {
	int nr;			/* Number of live bh's */
	int ratelimit;		/* Limit cacheline bouncing */
};

static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};

static void recalc_bh_state(void)
{
	int i;
	int tot = 0;

3305
	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
L
Linus Torvalds 已提交
3306
		return;
3307
	__this_cpu_write(bh_accounting.ratelimit, 0);
3308
	for_each_online_cpu(i)
L
Linus Torvalds 已提交
3309 3310 3311
		tot += per_cpu(bh_accounting, i).nr;
	buffer_heads_over_limit = (tot > max_buffer_heads);
}
3312

A
Al Viro 已提交
3313
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
L
Linus Torvalds 已提交
3314
{
3315
	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
L
Linus Torvalds 已提交
3316
	if (ret) {
C
Christoph Lameter 已提交
3317
		INIT_LIST_HEAD(&ret->b_assoc_buffers);
3318 3319
		preempt_disable();
		__this_cpu_inc(bh_accounting.nr);
L
Linus Torvalds 已提交
3320
		recalc_bh_state();
3321
		preempt_enable();
L
Linus Torvalds 已提交
3322 3323 3324 3325 3326 3327 3328 3329 3330
	}
	return ret;
}
EXPORT_SYMBOL(alloc_buffer_head);

void free_buffer_head(struct buffer_head *bh)
{
	BUG_ON(!list_empty(&bh->b_assoc_buffers));
	kmem_cache_free(bh_cachep, bh);
3331 3332
	preempt_disable();
	__this_cpu_dec(bh_accounting.nr);
L
Linus Torvalds 已提交
3333
	recalc_bh_state();
3334
	preempt_enable();
L
Linus Torvalds 已提交
3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346
}
EXPORT_SYMBOL(free_buffer_head);

static void buffer_exit_cpu(int cpu)
{
	int i;
	struct bh_lru *b = &per_cpu(bh_lrus, cpu);

	for (i = 0; i < BH_LRU_SIZE; i++) {
		brelse(b->bhs[i]);
		b->bhs[i] = NULL;
	}
3347
	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3348
	per_cpu(bh_accounting, cpu).nr = 0;
L
Linus Torvalds 已提交
3349 3350 3351 3352 3353
}

static int buffer_cpu_notify(struct notifier_block *self,
			      unsigned long action, void *hcpu)
{
3354
	if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
L
Linus Torvalds 已提交
3355 3356 3357 3358
		buffer_exit_cpu((unsigned long)hcpu);
	return NOTIFY_OK;
}

3359
/**
3360
 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378
 * @bh: struct buffer_head
 *
 * Return true if the buffer is up-to-date and false,
 * with the buffer locked, if not.
 */
int bh_uptodate_or_lock(struct buffer_head *bh)
{
	if (!buffer_uptodate(bh)) {
		lock_buffer(bh);
		if (!buffer_uptodate(bh))
			return 0;
		unlock_buffer(bh);
	}
	return 1;
}
EXPORT_SYMBOL(bh_uptodate_or_lock);

/**
3379
 * bh_submit_read - Submit a locked buffer for reading
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 * @bh: struct buffer_head
 *
 * Returns zero on success and -EIO on error.
 */
int bh_submit_read(struct buffer_head *bh)
{
	BUG_ON(!buffer_locked(bh));

	if (buffer_uptodate(bh)) {
		unlock_buffer(bh);
		return 0;
	}

	get_bh(bh);
	bh->b_end_io = end_buffer_read_sync;
	submit_bh(READ, bh);
	wait_on_buffer(bh);
	if (buffer_uptodate(bh))
		return 0;
	return -EIO;
}
EXPORT_SYMBOL(bh_submit_read);

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void __init buffer_init(void)
{
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	unsigned long nrpages;
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	bh_cachep = kmem_cache_create("buffer_head",
			sizeof(struct buffer_head), 0,
				(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
				SLAB_MEM_SPREAD),
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				NULL);
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	/*
	 * Limit the bh occupancy to 10% of ZONE_NORMAL
	 */
	nrpages = (nr_free_buffer_pages() * 10) / 100;
	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
	hotcpu_notifier(buffer_cpu_notify, 0);
}